GROWTH HORMONE-RELEASING HORMONE IN TESTICULAR INTERSTITIAL AND GERM-CELLS - POTENTIAL PARACRINE MODULATION OF FOLLICLE-STIMULATING-HORMONEACTION ON SERTOLI-CELL FUNCTION

GH-releasing hormone (GHRH) is present in the interstitial and germ ce lls of the rat testis. In previous studies we found that GHRH is secre ted from rat adult Leydig cells, in which it stimulates basal and LH-i nduced cAMP formation and steroidogenesis. In other studies cAMP produ ction in Sertoli cells was found to be stimulated by GHRH. In the pres ent report, we describe a potential paracrine action of GHRH in the Se rtoli cell, with stimulation of cAMP formation in cultured adult and p ubertal Sertoli cells. GHRH increased FSH-stimulated cAMP production i n adult and pubertal cultures in a time-dependent manner. GHRH stimula tion of basal and FSH-induced extracellular cAMP formation was more pr ominent in pubertal than in adult cultures. Immunocytochemical studies demonstrated the presence of GHRH-like immunoreactivity in rat inters titial cells from day 4 to adult life and in the acrosomal region of e arly and intermediate spermatids at stages III-VI of the seminiferous epithelium cycle. Immunoreactive GHRH was not observed in late spermat ids and mature sperm or in Sertoli cells at any age. These results ind icate that GHRH acts synergistically with FSH to promote cAMP producti on in Sertoli cells in culture. Testicular GHRH of Leydig and germ cel l origin may be an important paracrine regulator of Sertoli cell funct ion. Alternatively, GHRH present in germ cells may exert stage-specifi c intracrine functions.