Localization of luteinizing hormone, follicle-stimulating hormone, prolactin, and their receptors in human and rat testis using immunohistochemistry and radioreceptor assay.

Immunoperoxidase staining and radioreceptor assay were used to study the localization of LH, FSH, and PRL and their receptors in the human and rat testis. In immunohistochemical staining, the Leydig cells of both species were invariably LH positive and generally FSH negative, but there were some FSH positive cells which were morphologically indistinguishable from the Leydig cells. The tubules were LH negative. The Sertoli cells of both species were FSH positive, whereas the spermatogonia and other germ cells were negative. Positive staining for PRL was seen in rat Leydig cells, whereas the human testes were negative. In keeping with the immunohistochemical findings, LH and FSH receptors were found in the testis of both species, but PRL receptors only in the rat. The finding of FSH positive cells in the interstitial tissue may explain why FSH increases the number of Leydig cell LH receptors and increases the sensitivity and maximum response to LH stimulation. Failure to demonstrate PRL and PRL receptors in the human testis indicates either that very low receptor concentrations are needed to bring about PRL action or that the established testicular effects of PRL are indirect.