The secretion, measurement, and function of a testicular LHRH-like factor.

In this paper we have demonstrated the presence and secretion within the testis of a factor that is immunologically distinct from LHRH, but that has receptor-binding and bioactive features similar to LHRH. The major source of this LHRH-like factor is probably the Sertoli cell and, as its site of action appears to be restricted to the Leydig cells, it is possible that it is one of the means by which the Sertoli cell has been postulated to regulate the Leydig cell. All of the available evidence suggests that the action of the LHRH-like factor on the Leydig cell is inhibitory, and it may mediate some or all of the negative effects on the Leydig cell of LH and hCG. The precise role of the LHRH-like factor, particularly under physiological conditions (i.e., low level stimulation with LH), remains to be determined, but the availability of methods for its extraction, measurement, and inactivation should enable this problem to be resolved within the near future. Moreover, the recognition that Leydig cell function may be regulated by local factors within the testis should open up new avenues of research that may lead to improved methods for the regulation of fertility in the male.