Morphological study of the effects of an GnRH agonist on the canine testis after 4 months of treatment and recovery.

After 4 months of treatment of adult male dogs with the GnRH agonist (GnRH-A) [D-Trp6]GnRH ethylamide, the seminiferous tubules contained only type A and B spermatogonia, Sertoli cells, and rare primary spermatocytes, thus causing a 64% decrease in testis weight. At the electron microscope level, Sertoli cells showed an increase in phagosomes and lipid droplets. Leydig cells were markedly atrophied with the accumulation of lipid droplets and showed a predominance of mitochondria with lamellar instead of vesicular cristae. Four months after cessation of treatment with GnRH-A, a complete return to normal spermatogenesis and Leydig cell morphology was observed. The full reversibility of spermatogenesis in the dog after chronic GnRH-A treatment suggests that this well-tolerated peptide could be used as a reversible method of male contraception.