CA1089361A - Injectable male animal sterilant for selectively controlling the function of testes - Google Patents

Abstract

INJECTABLE MALE ANIMAL STERILANT FOR SELECTIVELY
CONTROLLING THE FUNCTION OF TESTES

Abstract of the Disclosure An injectable chemical compound capable of pro-ducing sterility in male animals having scrotal testes for use in selectively controlling the exocrine function of the testes in the production of sperm and the endocrine function in the production of testosterone. Said injectable chemical compound being a physiologically acceptable astringent, preferably a water soluble zinc compound, a tannin or com-binations thereof. Various concentrations of said compound being selectively injected directly into the testes or into the scrotum to suppress spermatogenesis and, optionally, to suppress production of testosterone.

Description

BACKGROUND OF THE INVENTION
1. Field of the Invention This invention relates generally to the field of drug, bio-affecting and body treating compositions, and more specifically to physiologically acceptable astringents for use in selectively controlling the exocrine function of the testes in the production of sperm and the endocrine function in the production of testosterone.

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2. Description of the Prior Art A large number and variety of chemical approaches have been tried to affect spermatogenesis in male animals. These approaches have included luteinizing hormones, testosterones, steroids and other steroidal derivatives. Examples of such compounds are described in U. S. patent ~o. 3,836,640.
In nearly all of these prior approaches, the compounds have been administered orally or injected into the body. None have proved chemically or commercially successful. Nearly all have failed because of adverse side ef,fects or reduction of libido.
The spermicidal effects of many non-essential metals are also known and have been comprehensively reported. Gunn, Samuel A. and Thelma Clarke Gould. 1970. The Testis, Vol. III, Influencing Factors, 377 - 481. Many of the metals studied are normally considered as toxic in any form.

3~1 The presence of zinc in the male reproduction process is well established, but its mode of action is not clearly defined.
Human seminal plasma normally contains a high concentration of zinc. Gallob-Hausmann, Gerda. Zinc and Its Physiological Relationship to the Human Body - A Review. However, there are indications that zinc ions under certain conditions can exert toxic effects on human spermatozoa. White, I. G. 1955. The Toxicity of Heavy Metals to Mammalian Spermatozoa. Austral. J.
Exp. Biol. 33, 359 - 366. Rosado, A., et al. 1970. Inhibition of Human Sperm Motility by Calcium and Zinc Ions. Contraception 2, 259 - 273. Kesseru, E., et al. 1972. Influence of Metals in In Vitro Sperm Migration in the Human Cervical Mucus.
Contraception 6, 231 - 240.
Zinc evidently plays a role in reproduction, appearing with carbonic anhydrase and alkaline phosphatase in the prostate and testes. The amount of zinc found in this tissue, however, is much higher than would normally be associated with the amount of these two enzymes present. Despite the large number of experiments demonstrating the presence and behavior of zinc in the male sex accessory organs, the function of this metal remains obscure. Byar, David P. 1974. Zinc in Male Sex Accessory Organs:
Distribution and Hormonal Response, Chapt. 6, Male Accessory Sex Organs - Structure and Function in Mammals.
- The toxic effects of zinc ions on human spermatozoa in vitro have also been studied. Lindholmer, C. 1974. Toxicity of Zinc Ions to Human Spermatozoa and the Influence of Albumin.
Andologia 6 (1), 7 - 16. The purpose of this study was to analyze the effects of zinc on the motility and survival of human spermatozoa, and to what extent these effects could be modified by albumin. Collected sperm cells were separated from the seminal i~385~
fluid by centrifugation and washed in a special solution. The washed cells were divided into two sample groups and 4% human albumin added to one group. A total concentration of 4~ albumin was chosen because this corresponds to the total protein concentration of human seminal fluid.
The test results showed that the addition of zinc at a concentration of 5 ug/ml (0.075 mM) to the samples without albumin markedly inhibited sperm motility. By contrast, the addition of zinc at a concentration of 50 ug/ml (0.75 mM) to the samples containing 4% albumin only slightly inhibited sperm motility. The protective effect of the albumin thus was clearly demonstrated.
It is presumed that with the concentration of albumin and zinc normally present in human semen, zinc albumin complexes are formed, some of which may precipitate on the cell surfaces.
The biological significance of such precipitate and coating complex is not known, but is assumed to be of importance for protecting the cells against toxic substances in the seminal fluid.

SUMMARY OF THE I~VE~TIO~
- The present invention is directed to the in vivo chemical control of spermtogenesis and the control of testosterone production in male animals having scrotal testes. This control is provided by the direct injection of a physiologically acceptable astringent into the testes or scrotum.
The effective control of spermatogenesis in the manner taught by this invention is accomplished without the undesirable side effects observed in the methods of the prior art.

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DETAILED DESCRIPTION OF THE INVENTION
The degree that spermatogenesis and testosterone production are inhibited depends upon the locus of the injection and upon the nature and amount of the astringent. In some cases, it is desirable to inhibit sperm production without affecting the production of testosterone. By a proper selection of astringent and place of injection, it is possible to stop sperm production without significantly affecting the interstitial cells which produce testosterone. It is the production of this male hormone which controls the animal's disposition, sex characteristics and libido.
~ uitable astringents are water soluble and are selected from those materials which precipitate proteins. When injected into the testes or scrotum, they must be capable of selectively inhibiting spermatogenesis and the production of testosterone.
They must also be physiologically acceptable and produce no undesirable toxic effects.
Such astringents if injected in the scrotum cause tanning of the tunica albuginea. Temperature regulation of the testes is interfered with by this hardening of the tunica which surrounds the testes. Since sex cells are susceptible to injury by a temperature equaling that of the interior body, such treatment provides a method for control of sperm production. In addition to hardening the tunica, some of the astringent penetrates the testes and has the same effect as if injected therein. Such effect, however, is relatively less since most of the astringent does not pass therein.
If injected into the testes, suitable astringents, on the cellular level, cause degeneration of the sex cells in the - ~ ' 3~jl seminiferous epithelium. This occurs through disintegration of the nuclear and cytoplasmic membranes of the sex cells. It is caused perhaps because the astringents disrupt the chemistry of the testicular fluid between the tubules and cause the tubules to have a hostile environment for the development of sex cells.
Depending upon the severity of treatment, the sex cells are progressively affected beginning at the lumen and extending to the periphery of the tubules. Preferably the Sertoli cells and basement membrane of the tubules are left intact, however, under very severe conditions, these are also affected.
If all of the sex cells are destroyed, the treatment is irreversible and results in the complete cessation of sperm production. If some of the sex cells are left, however, it is possible that the epithelium will regenerate and sperm production eventually resume.
In general, a smaller amount of astringent is necessary to stop sperm production if it is injected directly into the testes than if it is injected into the scrotum. Hence by selecting the dose and the locus of the injection, the sex cells can be selectively destroyed thus controlling the exocrine function of the testes in the production of sperm.
By selecting the dose and locus, the endocrine function can also be controlled. For example, it is possible by the present treatment to stop sperm production without affecting the Leydig cells in the stroma between the tubules. If it is desired to reduce the production of testosterone, it is possible to affect the Leydig cells by increasing the dose. This effect may be accomplished with a lesser amount if the astringent is injected directly into the testes.

The male hormone testosterone plays a vital role in the development of the male animal and controls the secondary sex characteristics, sex impulse and proper maintenance of the genital ducts and accessory glands. The present treatment provides a means for stopping sperm production without otherwise affecting the male, the size of his genitals or his libido. The present treatment optionally provides a means for complete castration if it is desired to stop the production of testosterone as well as the production of sperm. This may be desired, for example, for the purpose of changing the animal's disposition or for the purpose of shrinking his sex organs.
Most of the astringents for use as described above are tannins, zinc salts or combinations thereof. Suitable zinc salts include zinc acetate, zinc chloride and zinc sulfate. When the astringent is tannic acid, it is preferably predissolved in water and the insoluble precipitate of gallic acid separated therefrom by filtration. If a combination of tannic acid and zinc salt is used, it is preferred that an equal stoichiometric amount of each be used. So mixed, as injected, the effective astringent is zinc tannate.
It is preferred that the astringent solution be buffered to a pH from about ~.0 to about 6.5. This is because the pH of the solution affects the absorption and distribution of the drug throughout the scrotum and the testes. While such buffering is also desirable to avoid discomfort to the subject in the form of a stinging sensation, it is not necessary.
Before the astringent is injected, the scrotum should be cleaned with a disinfectant and the needle cleaned before the .

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injection of each testis. This is because the testes are very susceptible to infection.
The selected testis is palpated and the head and tail of t:he epididymis located. The injection is then given into the mid]ine of the testis. It is important that the injection not be given near the head of the epididymis so that the blood vessels are avoided as they enter the testis. If the injection is given into the blood vessels, the astringent coagulates the blood and forms a clot. It is also important that the injection not be given in the tail of the epididymis. This is because the astringent causes granuloma in fully matured sperm. When one testis has been injected, the other testis is palpated and an injection made into its midline.
The nerves in the testes follow the blood vessels but endings within the tubules seem doubtful. In any case, injection into the scrotum or into the testes does not cause the animal great discomfort.
The volume of the injection, however, does affect the subject's comfort. This is not so critical when the injection is into the scrotum but is highly critical when the injection is into the testes. If too large a volume is injected into the testes, the tubules are ruptured and the subject experiences pain.
The exact amount which can be injected depends, as aforementioned, on the locus of the injection as well as on the species of the animal and size of the particular subject's genitals. The proper amount in each case can be easily determined in view of the examples set forth below.

- i~)8~3f~1 The rollowlng examples and accompanylng draw-lngs lllustrate the lnvention. In the drawings, Flg. 1 ls a llght mlcrograph showing a h~istological section o~ a control rat testes; and Fig. 2 is a similar view arter treatment with zinc sulrate.
Example 1 Thls example lllustrates the er~ect Or zinc sulrate on male reproductlon Or sexually mature rats when administered orally.

Three hundred sexually mature rats were divided lnto three groups, Group I being a control. Group II rats were treated dally w~th 15.0 mg ZnSO4 7H2O and Group III rats with 50.0 mg, both groups receiving said treatment for 30 days. ~
As shown in Table 1, the data indlcate no sig-niricant change in the weight of the testes, epididymis, prostate or seminal veslcles. No histological changes were observed ln the male reproductive organs and no change in growth rate was observed.
As shown in Table 2, no slgniricant zinc concen-tratlon was round ln the blood and llver and no change was noted in testosterone levels.

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This example lllustrates the er~ect Or zlnc sulrate on male reproductlon Or sexually mature rats when admlnlstered lntraperitoneally.
Four hundred sexually mature rats were divided into ~our groups, Group I being a control. The rats in Groups II, III and IY were treated daily for 30 days, respectively, w~th 0.5, 1.0 and 5.0 mg ZnSO4 7H2O. At the end Or 60 days, as in Example 1, the rats were sacrirlced.
As shown in Table 3, there was no significant reductlon in the weight of the testes, epididym~s, prostate or seminal vesicles and no histological changes were ob-served in the sex organs as compared to the control.
There was, however, a signiricant reductlon ln the rate Or gain but the testosterone level was not changed.
A hlgher concentratlon o~ zlnc was ~ound ln the llver as shown in Table 4, ~ut the zinc concentration ln the testes, epldldymls,-prostate and-seminal vesicles was-substantially the same as ln the c~ntrol.

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--14 _ , 1~)8~?3~1 Example 3 .
This example lllustrates the ef~ect Or zin~
sul~ate on male reproduction ln sexually mature rats when admlnistered lnto the scrotum.
One hundred sexually mature rats were dlvlded lnto two groups, Group I being a control. Each Or the Group II rats was inJected with 25 mg ZnSO4~7H20 lnto each side Or the scrotum.
As shown in ~able 5, there was a slgnlrlcant reductlon in the welght Or the testes and epldldymis Or the treated rats. There was no difrerence, however~ in the weight Or the prostate and semlnal veslcles.
Histological examlnation Or the testes as shown in Figs. 1 and 2 showed a slgnlrlcant change in the con-; dition o~ the sex cells but no dl~rerence ln the condltion Or the Leydlg cells. This correlated wlth the finding that there was no significant reduction in testosterone levels as compared with the control.

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i E E ~ V- E ' ~ ~ E c 1~ ~ 'C v --16_ ~ 1()8~361 Example 4 Thls example illustrates the errect o~ zinc sulrate on male reproduction Or sexually mature rats when adminlstered ln the vas diferens.
Eighty sexually mature male rats were divlded lnto ~our groups, Group I being a control. The rats in Groups II, III and IV were treated by in~ectlng 0.5, 2.5 and 5.~ mg ZnS04-7H20 into the ~as dlferens.
At the end Or 60 days, as in the other examples, the rats were sacrificed. There was no signiricant change in the weight of the testes, prostate or seminal vesicle3 and no efrect on spermatogenesis There was an increase in the weight Or the epididymls, however, ln the Group IV
rats due to the development Or sperm granulomas.

Example 5 This example illustrates the efrect Or zinc sul~ate on male reproductlon o~ sexually mature rats when administered in the testes.
Four hundred sexually mature male rats were - divided into rour groups, Group I being a control. The rats in Groups II, III and IV were treated by in~ecting 0.5~ 2.5 and 5.0 mg ZnS04-7H20 into the testes. Such ln~ectlon was made into the midline Or each testls with a sterillzed needle.
The results Or this example showed a signiflcant 3 reduction in the ~:eight Or the male reproductive or~ans, partlcularly ln that of the testes and prostate. The amount Or reduction lncreased with the dose administered 185~3~1 and was correlated with a decrease in the testosterone level.
All of the animals from Examples 1 - 5 were mated with females in heat. Those rats which were treated orally (Example 1) or intraperitoneally (Example 2) with zinc sulfate impregnated the females. Pregnancy also occurred from those animals which had received 0.5 and 2.5 mg ZnSO .7H o in the vas deferens while those animals treated with 5.0 mg did not impregnate the females due to sperm granuloma of the epididymis (Example 4). No pregnancy resulted from any of the rats treated in Examples 3 and 5. Only Examples 3 and 5 are in accordance with the present invention.
Examples 1, 2 and 4 were conducted for the purpose of comparison.
Example 6 This example illustrates a treatment wherein spermatogenesis is stopped without reducing the weight of the testes. This is desired, for example, by some pet owners and usually when the subject is a human male.
Ninety sexually mature male rats were divided into two groups, Group I being a control. The rats in Group II were treated by injecting 0.05 ml into each testis of a drug, herein called Kastrin and containing about an equal amount of zinc sulfate and tannic acid, more particularly containing in this instance 0.25 mg of tannic acid and 0.25 mg of ZnSO .7H O.
All of the anima]s were mated with a female in heat. None of the treated rats impregnated the fe-males. When the rats were sacrificed, it was found that there was no significant difference in the weight of the reproductive organs and that the testosterone levels were not - 1a)893f~1 slgniricantly dlrrerent rrom the control group.
Example 7 , As in Example 6, 90 sexually mature rats were dlvlded into two groups 9 Group I belng a control. The rats ln Group II were lnJected wlth a mlxture o~ zinc sulrate and tannic acid such that 2.5 mg of tannlc acld and 2.5 mg o~ ZnS04.7H20was ln~ected lnto each testis.
The treated rats ln Group II were sterile, had smaller testes but there was no change ln the testosterone levels as compared to the control group.
Example 8 As in Examples 6 and 7, 90 sexually mature rats were divided into two groups, Group I being a control. The rats in Group II were in~ected wlth a mixture of zinc sul-rate and tannic acid such that 5.0 mg Or tannic acid and 5.0 mg o~ ZnS04-7H20 was lnJected into each testls.-The treated rats ln Group II were sterile, had smaller reproductive organs and-lower testosterone levels as compared to the control animals. More particularly, the testosterone level Or Group I was 8.2 ~ o.46 ng~ml as compared to less than 1 ng/ml in the treated animals.
All of the treated animals ln Examples 6, 7 and 8 were ~ept for a year with no mortalit~. When they were sacrl~iced, none had abnormal organs, liver, kidney, ad-renal, lung or pltuitary and no toxic side effect was noted whatsoever.
Example 9 . _ As in the previous examples, sexually mature rats were divided into two groups, &roup I being a control. The 3 Group II rats were in~ected with a mlxture Or zinc sulfate and tannic acid such that 5.0 mg o~ tannic acld and 5.0 mg 3~
Or ZnS04-7H20 was lnJected into each slde o~ the scrotum lnto the cavity Or the tunlca vaglnalls.
The treated rats ln Group II were sterlle and were kept for a year wlth no mortality. When they were sacrlficed, there was no reductlon in the welght Or ~he prostate or ln the testosterone level as compared to the rats in the control.
When the results Or this example are compared w~th those in Example 8, it is seen that the efrect on the endocrine function Or the testès is more pronounced when the in~ection ls into the testes as compared to the scrotum.

Example 10 The rats ln this example were divided and treated as ln Example ~ except that the amount of tannlc acld and zinc sul~ate in~ected into each side Or the scrotum was doubled.--As ln Example 9, all Or the treated rats were sterlle. When the rats were sacrlriced, however, there was found a reduction in the weight Or all Or the reproductive organs and-a signiricant-reductlon~in the testosterone levels in the blood.
Thus lt ls seen that the same effect on the testes can be had by inJecting an astrlngent lnto the scrotum or into the testes. The amount necessary to achieve a reduc-tion in the endocrine ~unction, however, is more when the drug is inJected lnto the scrotum.

EYample 11 Six dogs weighing 15 to 22 kg and a~ing between 3 8 and 11 years were in~ected ln each testls with 1.0 ml o~
a mixture contalning 100.0 mg Or tannic acid and 100.0 mg o~ ZnS04 7H20. Berore treatment, two Or the dogs were diag-1~893t~ .

nosed with hyperplasla Or the prostate, the others with adenocarcinoma. Dlagnosls was achleved by rectal and abdomlnal palpatlon and by prostate blopsy. All had dirflculties in urlnation.
Each dog was examlned weekly. After one month, the prostate was shrunk in slze and the animal was albe to urinate normally. Thus, surglcal castratlon was made unnecessary and avoided.
This example shows that by controlllng the endo-crine function Or the testes in their product~on Or testo-sterone a chemlcal method is provlded ror the treatment Or the prostate. In human males, as in dogs~ chronlc pro- ¦
statitis, benlgn hyperplasia and adenocarcinoma o~ the pro-state are common diseases. The present treatment provides a convenient, relatlvely risk free, alternative to surgery.
Example lZ
-Two-hundred 30-day old male rats, ~ust weaned, were divlded lnto rour groups, Group I being a control. The rats in Group I were inJected with 0.05 ml Or water into each testis. The rats in Group II were similarly in~ected ; with 5.0 mg-~~or ZnS0~ 7H20-, those in-Group-III-~with 5.0 mg Or tannic acid and those in Group IV with a mixture tKastrin) 1-contalning 2.5 mg tannic acid and 2.5 mg ZnS04-7H20. ;
The data from this exam"le are reprted in Table 6. Forty Or the animals were sacrificed 60 days after treatment. The others were watched for a year. The results showed that all Or the treated rats were sterile. There was no signlrlcant change in the rate of gain.

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Example 13 Thirty~eight litter mate dogs, 8 weeks old, wlere divided lnto four groups. The dogs in Group I were a control and were ln~eeted with 0.2 ml Or water into each testis. The animals ln Group II were similarly treated in each testis with 20.0 mg Or tannic acid ~urrered to a pH Or 6-~-Those in Group III were treated with 20 mg Or ZnS04 7H20 and those ln Group IY with a mixture Or 10 mg Or tannic acld and 10 mg Or ZnS04-7H20.
None Or the treated animals impregnated ~emaleswhen they reached the age Or sexual maturity. There were no signlricant di~rerences, however, in the rate Or growth, development of the urinary tract or development Or the pelvic bones as documented by x-ray. In ract, the dogs in Group II which were treated with tannic acid showed better muscular appearance than those in the control group.
Two years arter treatment, all Or the dogs in Groups II, III and IV~were healthy, active and showed no adverse side e~fects whatsoever. The only dirrerence be- -¦
tween them and those in the control was that the treated -dogs were sterile and had smaller testes. There was, how-ever, no difrerence in libldo.
Example 14 Firty sexually mature dogs were divided into two groups. ~lentyJ each weighing less than 15 kgj were in-~ected in each testis with 0.5 ml Or an aqueous mixture containing 2.5 mg o~ tannic acid and 2.5 mg Or ZnS04-7H20.
The remaining dogs, each welghing between 20 and 35 kg, ~ere in~ected in each testis with 1.0 ml Or a mixture containing 3 5.0 mg Or tannic acid and 5.0 mg Or ZnS04-7H20.
~erore treatment, the semen Or each dog was evalu-ated. On average, the volume was 5.5 ml, the motility 4~, 10893~1 the sperm count 400 x 106/ml, the pH 6.2 and the mor-phology 4% wlth coiled talls and 2% tallless wlth 8 to 10% dead.
~ Forty eight hours arter treatment, the semen Or each dog was again evaluated. On average, the volume was 5.5 to 6.0 ml, the motility 1~, the sperm count 400 x 106/
ml, the pH 6.3 and the morphology 70% wlth co~led tails and 20% tallless with 100S dead. Arter one week, the vol-ume was 4.0 ml, the motlllty 0, the sperm count 10 x 106/
ml, the pH 6.2 and the morphology 96% wlth colled tails and

4% tallless wlth 100~ dead.
The semen Or each dog was evaluated agaln a~ter two weeks, one month, three months, six months, one year and two years. In each case, no live sperm were found.
Needle testicular biopsies were taken before treatment, ten months after and two years after. Histological examlnat~on showed the absence of spermatogenesis arter ~
treatment as compared to the normal conditlon exlstlng be-ore. Example 15 Sexually mature dogs were treated in thls example as in Example 14 except that they were in~ected in each testis with 0.1 ml Or a solution containing 5 . a mg Or tan-nic acid and 5.0 mg Or ZnS04-7H20.
One week arter treatment, the sperm count drop-ped rrom 400 x 106 to 1-5 x 106~ml. Six months after treatment, the sperm count had recovered somewhat to 10 x 106/ml. At the end Or two ~ears, the sperm count was substantiall~ no~mal.
Other dogs which had been repeatedly in~ected with the same amount of the drug were made permanently sterile~
3 Th~s example lllustrates that by controlling the dose, the exocrine functlon Or the testes can ~e inhibited 10893~i1 temporarily. It also lllustrates that a do9e lnsufrlclent to cause permanent sterllity lr admlnistered only once can 'Lnduce permanent sterlllty 1~ admlnlstered several tlmes.
Example 16 Thirty sexually mature cats welghlng 4.3 + 0.2 kg were dlvided into three groups, Group I being a control.
Those animals ln Group I were in~ected ln each testls wlth 0.1 ml Or water. Those ln Group II were lnJected wlth 10.0 mg o~ tannic acld bu~rered to a pH o~ 6.8 and those in Group III wlth 5.0 mg Or tannic acld and 5.0 mg o~ ZnSO4 7H2O.
Berore treatment and a~ter ln the case of the con-trol group, the average sperm count was 230 x 106~ml. One week a~ter treatment, the sperm count for the anlmals ln Groups II and III was zero.
All Or the anlmals were observed for one year and bred with ~emale cats ln the spring and rail. None Or the treated animals impregnated the ~emale~s. The testo-sterone_level for the cats in Group I was 6.8 ~ 0.2 ng/ml, or those ln Group II 4.1 + 0.3 ng/ml and less than 1 ngfml ror those in Group III.
The cats ln Groups I and II acted normally but those ln Group III exhiblted no normal male aggresslveness.
The urine Or Group III also lacked characteristlc odor.
None Or the animals ln Groups II or IIIgained any more welght than those in Group I. In other words~ the treated anlmals did not become obese llXe surglcally castrated ani-~` mals.
Exam~l~ 17 Ten purebred Angus bulls weighing an avera~e of 40 pounds were dlvided into ~ive groups, Group I being a control. Each anlmal in Group I was inJected w~th 5.0 ml 10893~1 -- Or water in each testls. Those ln Group II were surglcally castrated. The anlmals in Group III were lnJected with 500.0 mg Or tannic acid, those ln Group IV with 500.0 mg Or ZnS04-7H20 and those in Group V with 250.0 mg o~ tannic acid and 250.0 mg Or ZnS04-7H20.
The animals were red concentrate and grazed.
After one year, they were sacririced. All Or the anlmals passed ~ederal inspection ror consumption by h~mans.
As shown in Table 7, all Or the animals in Groups III, IV and V had a raster rate Or gain than the surgically castrated anlmals in Group II. The animals in Group V
had better carcass quality than that Or any other group.
No signirlcant concentrations Or zinc or tannic acid were round ln the muscle, blood, spleen, heart, liver or kidney Or the treated anlmals as compared to Groups I and II.
~he data there~ore indlcate that the~present--treatment-provides~a safe means ror castrat-ing~cattle, which ~~~~
in some instances provldes better rate Or gain and carcass quality as compared to surglcal castration.

-2Ç-1~89361 Table 7 BODY WEIGHT
TREATMENT Initlal Final Rate Or Gain %Protein ~Fat Group I 384 960 1.79 lbs/day 17.0 24.0 Group II 498 912 1.29 lbs/day 18.I 19.5 Group III 376 826 1. 40 lbs/day 18.3 18.0 Group IV 414 910 1.54 lbs/day 17.9 20.9 Group Y 406 1062 2.04 lbs/day 17.7 22.5 .. .. . .

.

-- -- - - -- - - .... _=.

!

, .

108~361 In additlon to the above, the present treatment can be used on male sheep, pigs, horses and other slmllar ma~nals havlng scrotal testes, includlng human males.
Recommended dosages, as above mentloned, depend upon the size and species Or the animal and upon the de-sired result. Recommended dosages ror sterilization Or adult dogs weighing less than 10 ~g is 0.25 ml lnto each testls o~ a mixture containing between 10.0 and 25.0 mg o~
tannlc acid and 25.0 mg Or ZnS04-7H20. For dogs welghlng between 10 and 15 kg, the recommended dose ls 0.5 ml lnto each testis Or a mixture contalning between 10.0 and 50.0 mg o~ tannic acid and 50.0 mg Or ZnS04 7H20. For those dogs weighing between 16 and 20 kg, the recommended dose is 1.0 ml into each testls Or a mlxture-containlng between 50.0 and 100.0 mg Or tannlc acid and between 75.0 and 100.0 mg Or ZnS04-7H20. For dogs weighlng over 20 kg, the recommended dose::ls-l.0 ml in''each testl-s~o~--a mixture-containing between 50.'0 and--125.0 I-ng Or tannic acid and l25.0-mg Or ZnSo4-7H20.
In the case Or pupples between 6 and 8 weeks o~
age, the recommended dose ls 0.05 ml lnto each testls Or a mixture containlng 2.0 mg Or tannlc acld'and 5.0 mg o~
ZnS04-7H20. For puppies over 8 weeks but not sexually mature, the dose is prererably o.o8 ml into each of the testes Or a mixture containing 7.0 mg Or tannic acid and 7.0 mg Or ZnS04-7H20. For adult cats, the recommended dose is 0.1 ml into each testis o~ a mixture containing 10.0 mg Or tannic acld and 10.0 mg Or ZnS04 7H20.
When tannic acid and zinc sulfate are administered ln each testis in the above-mentloned reco~nended amounts, the treatmenc has been found ef~ective to arrest spermato-genesis. Since zinc is normally present ln semlnal fluid, _ 28 -108~3~1 ~uch treatment adds a mlnimum Or rorelgn materlal to the body o~ the anlmal. Moreover, the drug remalns substantl-ally localized in the lmmedlate area Or the in~ectionO When the astringent ls zinc sulrate, ror example, there ls some dirruslon Or the zlnc to the epididymis and prostate, but no dlrruslon beyond that. When the astrlngent ls a com-blnatlon Or a zinc compound and a tannin, there is even less tendency ror the zinc to difruse. Such combinations are, ror that reason, prererred.
Most Or the experimental work reported in the above examples was per~ormed by in~ection Or the drugs with a needle. It is to be understood that other means Or sub-cutaneous penetratlon may also be employed as desired.
In view Or the above, it will be seen that the séveral ob~ects Or the lnvention are achieved and other advantageous results attained. More partlcularly, a chemi-cal compound and treatment is taught whereby the exocrine and endocrine runction Or the testes are controlled.
As varlous changes could be made in the above described compounds and treatemnt wlthout departing rrom the scope Or the invention, lt is intended that all matter contained ln the above descriptlon or shown ln the accom-panylng dra~ings shall be lnterpreted as illustrative and not in a llmlting sense.

Claims (11)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An injectable chemical sterilant for injection into the testes or scrotum of male animals having scrotal testes, said chemical sterilant having activity for selectively inhibiting spermatogenesis and the production of testosterone, consisting of a mixture of an effective amount of a water soluble physiologically acceptable zinc compound capable of selectively inhibiting spermatogenesis and the pro-duction of testosterone and an effective amount of a water soluble physiologically acceptable tannin capable of combining with the zinc compound to inhibit the transport of zinc from the testes or scrotum of the subject male animal in water solution buffered to a pH from about 4.0 to about 6.5.

2. The injectable chemical sterilant according to claim 1 wherein the zinc compound and the tannin are present in substantially stoichiometrical amounts.

3. The injectable chemical sterilant according to claim 2 wherein the zinc compound is a member selected from the group consisting of zinc acetate, zinc chloride and zinc sulfate

4. The injectable chemical sterilant according to claim 3 wherein the tannin is tannic acid

5. The injectable chemical sterilant according to claim 4 wherein the zinc compound is zinc sulfate.

6. The injectable chemical sterilant according to claim S
wherein substantially any impurity of gallic acid is removed from the tannic acid before said mixture is formed.

7. The injectable chemical sterilant according to claim 6 wherein a dose for injection into each testis contains the zinc sulfate in an amount from about 5 mg to 125-mg as ZnSO4?7H2O and contains the tannic acid in an amount from about 2 mg to 125 mg.

8. The injectable chemical sterilant according to claim 7 for use with adult dogs wherein the dose is present in a volume from about 0.25 ml to about 1.0 ml.

9. The injectable chemical sterilant according to claim 7 for use with puppies between 6 and 8 weeks of age wherein the dose is present in a volume about 0.05 ml.

10. The injectable chemical sterilant according to claim 7 for use with puppies over 8 weeks of age but not sexually mature wherein the dose is present in a volume about 0.08 ml.

11. The injectable chemical sterilant according to claim 7 for use with adult cats wherein the dose is present in a volume about 0.1 ml.