RESUMO
The objective was to evaluate the efficacy of a single intratesticular injection of a Zinc Gluconate-based solution to induce sterility in male dogs. Fifteen pubertal mongrel dogs (8 mo to 4 y old) were assigned to two groups; Control dogs (n = 5) received a single injection of an isotonic saline solution into each testis, whereas Treated dogs (n = 10), were given Testoblock, a proprietary zinc-gluconate (13.1 mg zinc/ml) solution in a physiological vehicle. The volume of saline or Testoblock injected varied from 0.2 to 1.0 ml/testis (based on testis width). Physical examination, testis width, hematology, clinical chemistry (hepatic and renal function), plasma testosterone concentration, semen characteristics, and libido, were assessed until castration (150 d after treatment). In Treated dogs, testis width increased (approximately 20%) relative to that in Control dogs, but subsequently was not significantly different from Controls (group × time interaction, P < 0.0001). For all dogs, values for hematology and clinical chemistry consistently remained within reference ranges. Although plasma testosterone concentrations decreased over time (P < 0.006), there was only a tendency for an effect of group (P < 0.09), and libido was not significantly affected. By 63 d after Testoblock treatment, eight Treated dogs were azoospermic, whereas the remaining two were oligozoospermic (<10 × 10(6) sperm/ml). We concluded that intratesticular injection of the Zinc Gluconate-based chemical sterilant Testoblock has considerable potential to induce permanent contraception in male dogs.
Assuntos
Anticoncepcionais Masculinos/uso terapêutico , Gluconatos/uso terapêutico , Esterilização Reprodutiva/veterinária , Testículo/efeitos dos fármacos , Animais , Anticoncepcionais Masculinos/administração & dosagem , Gluconatos/administração & dosagem , Injeções/veterinária , Libido/efeitos dos fármacos , Masculino , Espermatogênese/efeitos dos fármacos , Esterilização Reprodutiva/métodos , Testículo/anatomia & histologia , Testosterona/sangueRESUMO
Background: Fertility control of animals by nonsurgical methods has been pursued to prevent unwanted pregnancies and suppress testosterone-dependent traits in farm and companion animals. In the latter, injection of sclerosing agents into the testis had considerable potential as a candidate for chemical sterilization of dogs. This article aims to review the potential of this new non-surgical technology for sterilization of male dogs. Review: Investigations of contraceptive agents for male dogs where initiated only in the last decade. Chemical sterilization is a solution for pet overpopulation and for non-surgical methods of male contraception. A variety of compounds have been tested, some of which were either safe but not effective or vice versa. The ideal chemical sterilization needs to meet three key criteria to be regarded as a good alternative to surgical sterilization. First, it has to be effective in a high percentage of treated animals. Secondly, it should have a high margin of safety for treated animals and the environment. Third, it has to be permanent and irreversible following a single treatment. The first product obviously fulfilling these criteria was zinc gluconate. Conclusion: Intratesticular injection of a zinc gluconate-based solution has great potential as a permanent contraceptive for dogs.
Assuntos
Animais , Masculino , Cães , Zinco/administração & dosagem , Anticoncepcionais Masculinos/análise , Gluconatos/administração & dosagem , Soluções Esclerosantes/administração & dosagemRESUMO
The objective of the present study was to evaluate, by light and transmission electron microscopy, the efficacy of a single intratesticular injection of a novel zinc-based solution, as a contraceptive for male dogs. Fifteen mongrel dogs were assigned to three groups (five dogs/group). Group 1, the control group, which consisted of animals ranging from 8 mo to 4 yr, was injected with saline solution. Group 2, which consisted of animals ranging from 8 mo to 1 yr old and Group 3, animals ranging from 2 to 4 yr old, were injected with a zinc-based solution (0.2-1.0mL; volume based on testicular width). There were no histopathological changes detected in testes from control dogs. Histological examination of treated groups revealed degeneration, vacuolation, fewer germ cells, formation of multinucleated giant cells, and a lack of elongated spermatids in atrophic seminiferous tubules. Leydig cells had varying degrees of lipid degeneration and necrosis. The majority of seminiferous tubules in all zinc-treated dogs were lined only by Sertoli cells, which were vacuolated. Ultrastructure of testis of treated groups had degenerate Sertoli and Leydig cells, characterized by numerous mitochondria with the lack of a matrix and agglomeration of lysosomal bodies. The cytoplasm of elongated spermatids was characterized by tubules of hyperplastic and hypertrophic smooth endoplasmic reticulum and numerous Golgi apparati. Round spermatids in Golgi phase had lysis of acrosomal vesicles. The degree of histological changes suggested irreversibility. In conclusion, intratesticular injection of a zinc-based solution effectively impaired spermatogenesis.