Abstract
Intratesticular injection of 3 µg ovine FSH or 1 µg rat FSH caused a 50% decrease in the number of FSH binding sites available 24 h after injection in immature rats aged 16-17 days. Measurement of injected hormone bound in vivo, by radioimmunoassay of FSH released from testes incubated at 65°C for 30 min in vitro, showed that this effect was not due to receptor occupation. FSH-sensitive cyclic AMP (cAMP) production in whole cells showed a similar decrease 24 h after FSH injection. In cell-free homogenate of tubular cells isolated from testes injected 24 h earlier with FSH, there was a reduction in the Vmax of FSH-sensitive adenylate cyclase with no change in Km.