Suppression of pituitary-testis function in rats treated neonatally with a gonadotrophin-releasing hormone agonist and antagonist: acute and long-term effects

Abstract

The acute and long-term effects of pituitary-testis suppression with a gonadotrophin-releasing hormone (GnRH) agonist, D-Ser(Bu(t))6des-Gly10-GnRH N-ethylamide (buserelin; 0.02, 0.1, 1.0 or 10 mg/kg body weight per day s.c.) or antagonist, N-Ac-D-Nal(2)1,D-p-Cl-Phe2,D-Trp3,D-hArg(Et2)6,D-Ala10 -GnRH (RS 68439; 2 mg/kg body weight per day s.c.) were studied in male rats treated on days 1-15 of life. The animals were killed on day 16 (acute effects) or as adults (130-160 days; long-term effects). Acutely, the lowest dose of the agonist decreased pituitary FSH content and testicular LH receptors, but with increasing doses pituitary and serum LH concentrations, intratesticular testosterone content and weights of testes were also suppressed (P less than 0.05-0.01). No decrease was found in serum FSH or in weights of accessory sex organs even with the highest dose of the agonist, the latter finding indicating continuing secretion of androgens. The GnRH antagonist treatment suppressed pituitary LH and FSH contents and serum LH (P less than 0.05-0.01) but, as with the agonist, serum FSH remained unaltered. Testicular testosterone and testis weights were decreased (P less than 0.01) but testicular LH receptors remained unchanged. Moreover, the seminal vesicle and ventral prostate weights were reduced, in contrast to the effects of the agonists. Pituitary LH and FSH contents had recovered in all adult rats treated neonatally with agonist and there was no effect on serum LH and testosterone concentrations or on fertility.(ABSTRACT TRUNCATED AT 250 WORDS)