Developmental pattern of the testicular androgen response to gonadotrophin stimulation in vitro and its modification by chronic hypoprolactinaemia.

Developing male rats were treated chronically with bromocriptine (BR, 3 mg/kg b.w. daily) to maintain severe hypoprolactinaemia throughout postnatal development. This treatment induced a precocious increase in Leydig cell numbers per testis and caused substantial, but age-dependent, modifications of the androgenic responsiveness of incubated hemi-testis preparations to stimulation with hCG. Most conspicuous were: (i) a decrease in sensitivity of the testis to hCG at the approach of adult age (due presumably to reduced responsiveness of the Leydig cells), and (ii) a precocious increase in the steroidogenic maximum of the testis at peripubertal age. This probably resulted from the precocious increase in Leydig cell numbers, which was able to mask the negative consequences of reduced androgenic capacity per Leydig cell. The precocious increase in number of Leydig cells induced by hypoprolactinaemia could have resulted from facilitation of the proliferative action of the high prepubertal LH levels on Leydig cell numbers. There were no clear-cut indications for an important effect of BR-induced changes in LH levels, or of a direct effect of BR on the testis.