Response of immature, mature nonbreeding and mature breeding ferret testis to exogenous LH stimulation.

Abstract

The responses of immature mature nonbreeding and mature breeding ferret testis to exogenous luteinizing hormone (LH) stimulation are reported. Plasma testosterone concentrations were compared after LH was administered by im injection at doses of 10 and 100 mcg/kg body weight. Mature breeding animals revealed a variable response dependent on their plasma testosterone levels prior to injection. Those with high preinjection testosterone levels (25-30 ng/ml) showed little response suggesting that their testes were already maximally stimulated. Mature nonbreeding animals responded to both LH doses with elevated plasma testosterone levelsconsistent with those in sexually active males (15-27 mg/ml). 100 mcg of LH produced a higher and more sustained response than 10 mcg. Immature ferret testes revealed a small transitory response to both doses but their plasma testosterone levels did not approach those found in sexually active ferrets. These data indicate that increase in responsiveness of the ferret testis to LH may be an important factor in puberty while variation in level of LH secretion may be responsible for annual recrudescence of mature males.