Effects of prolactin on luteinizing hormone-stimulated testosterone secretion in isolated perfused rat testis.

The direct peripheral effect of prolactin on LH-stimulated testosterone secretion was re-evaluated using the intact, isolated, perfused rat testis. In paired experiments, one testis was infused with the hormones being studied; the other testis of the same rat was used as the control. A dose-response curve of LH-stimulated testosterone secretion was established first. A dose of 300 ng of LH, which was on the ascending portion of the dose-response curve, was selected so that both stimulatory and inhibitory effects of prolactin could be observed. Prolactin doses ranging from 0 ng to 3000 ng were then tested to determine alterations in LH-stimulated testosterone secretion. Prolactin inhibited LH-stimulated testosterone secretion at low doses (less than 300 ng), but augmented LH action at high doses (greater than 1000 ng). These results showed that prolactin and LH interact with each other in a biphasic dose-dependent manner.