REVERSIBLE SUPPRESSION OF PITUITARY-TESTICULAR FUNCTION BY A SUSTAINED-RELEASE FORMULATION OF A GNRH AGONIST (LEUPROLIDE ACETATE) IN DOGS

摘要

Pituitary-testicular function was studied in 15 dogs following treatment with a sustained-release formulation of a GnRH agonist, leuprolide acetate (LA). Adult male dogs were treated with a single subcutaneous injection of microencapsulated LA (0.1 or 1 mg/kg). Treatment with LA at a dose of 1 mg/kg resulted in decreased (P<0.001) ejaculatory volume and disappearance of morphologically normal spermatozoa within 8 wk and the effect persisted for 6 wk, while the 0.1 mg/kg dose was not adequate to effect suppression of spermatogenesis. The larger dose treatment (1 mg/kg) caused a transient rise in plasma levels of LH and testosterone followed by a marked decline to below the normal level by 2 wk, the low levels being maintained for at least 5 wk, indicating a prolonged effect of LA treatment on pituitary-gonadal axis. Twenty weeks after treatment with LA, a complete return to normal spermatogenesis was observed. The full reversibility of spermatogenesis in the dog after LA treatment suggests that this peptide could be used as a reversible method of male contraception.