RESUMO
Male sterilization by chemical agents is a nonsurgical contraceptive approach designed to induce azoospermia and, therefore, infertility. Intratesticular injection of zinc gluconate for sterilization of dogs has been described, but its use in cats remains limited. The objective of the present study was to evaluate, by light and transmission electron microscopy, the efficacy of a single intratesticular injection of a zinc gluconate solution (Testoblock) as a sterilant for male cats. Twelve sexually mature mixed breed cats were allocated at random into two groups (control = 6; treated = 6) and given a single injection into each testis of either isotonic saline or zinc gluconate, respectively. Histopathologic and ultrastructural evaluation was assessed at 120 days postinjection. Histopathologic changes were not detected in the testes from the control group. However, histologic evaluation of the treated group revealed atrophic and dilated seminiferous tubules, a decrease in the number of germ cells, and incomplete spermatogenesis. Sertoli cells had various degrees of cytoplasmic vacuolization. Intertubular tissue revealed active fibroblasts, collagen deposition, and inflammatory cells. The diameter of seminiferous tubules, epithelial height and tubular area were reduced (P < 0.05) in the treated group compared with controls. Azoospermia occurred in 8 of the 11 treated cats (73%). Ultrastructural evaluation of Leydig cells revealed loss of nuclear chromatin, increased smooth endoplasmatic reticulum, and mitochondria degeneration. Intratesticular injection of zinc gluconate solution impaired spermatogenesis in cats and has great potential as a permanent sterilant in this species.
Assuntos
Castração/veterinária , Gatos/fisiologia , Anticoncepção/veterinária , Anticoncepcionais Masculinos/uso terapêutico , Gluconatos/uso terapêutico , Espermatogênese/efeitos dos fármacos , Testículo/efeitos dos fármacos , Animais , Castração/métodos , Anticoncepção/métodos , Anticoncepcionais Masculinos/efeitos adversos , Gluconatos/efeitos adversos , Masculino , Microscopia Eletrônica de Transmissão , Testículo/ultraestrutura , Testosterona/sangueRESUMO
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.