Effect of a powerful antagonist of LH-RH on testicular function in prepubertal male rats

The effects of N-Ac-D-p-F-Phe1,D-p-Cl-Phe2,D-Trp3,6,D-Ala10-LH-RH, a new antagonistic analog of LH-RH, were tested on the testicular function and serum FSH and LH levels in immature male rats. Prolonged administration of this analog to prepubertal male rats resulted in lower testicular and seminal vesicle weights as compared with control rats treated with the vehicle only. Spermatogenesis was markedly delayed in rats injected with the analog. Serum FSH and LH levels were significantly lower in the analog-treated rats as compared to the controls. These data show that LH-RH antagonists may be useful for inhibition of spermatogenesis.