Synergistic action of follicle-stimulating hormone and testosterone on radioactive phosphorus incorporation into testes of the immature Japanese quail.

Injections of 2 to 80 μg of NIH-FSH-S12 induced a log-dose-dependent increase in the ³²P incorporation into testes of newly hatched cockerels of the Japanese quail, but injections of 4 μg of NIH-LH-S19 did not. Injections of 2 mg of testosterone increased the response of the Japanese quail cockerel to FSH. Both the level of the incorporation and the slope of the dose-response curve were increased by the treatment. Treatment with testosterone alone induced no or slight response. The potentiation of the effect of FSH by testosterone is considered to be due to the increase in the density of FSH receptors induced by testosterone, since Ishii and Tsutsui (1978, Gen. Comp. Endocrinol.36, 297–305) recently found that administration of testosterone or testosterone and FSH increased the density of FSH receptors in the testis of immature Japanese quails.