CORTICOTROPIN-RELEASING FACTOR (CRF) AGONISTS STIMULATE TESTOSTERONE PRODUCTION IN MOUSE LEYDIG-CELLS THROUGH CRF RECEPTOR-1

The influence of CRF on testosterone production in primary mouse Leydi g cell cultures was studied, and the type of CRF receptor (CRF-R) invo lved in this activity was determined. CRF directly stimulated testoste rone production in mouse Leydig cells, but did not influence the maxim um human (h)CG-induced testosterone produc tion. The effect was time-a nd dose-dependent, saturable with an EC,, of 2.84 nM for hCRF, antagon ized by the CRF antagonist alpha-helical CRF9-41, and accompanied by i ntracellular cAMP elevation. The rank order of potency of the natural CRF agonists, hCRF, ovine CRF, sauvagine, and urotensin, corresponded to that of their activities on CRF-R1 in rat pituitary cells and also to that reported for this receptor, but not for CRF-RB, when transfect ed into various cell lines. Furthermore, the difference in response of mouse Leydig cells to [11-D-Thr,12-D-Phe]- and [13-D-His,14-D-Leu]-ov ine CRF corresponded to that measured when COS cells expressing CRF-R1 were activated, but was considerably smaller than that observed for a ctivation of COS cells expressing CRF-R2 alpha or -R2 beta. The messen ger RNA encoding the mouse CRF-R1 was detected by RT-PCR in mouse Leyd ig cell preparations. In contrast to mouse Leydig cells, CRF agonists had no influence on the basal testosterone and cAMP production by rat Leydig cells, nor did the agonists or antagonist change the hCG-stimul ated testosterone and cAMP production by these cells. It is concluded that mouse Leydig cells express CRF-R1, mediating elevation of testost erone production by CRF agonists through cAMP. Because potencies of CR F agonists in activating mouse Leydig cells were more than 10-fold low er compared with their potencies in stimulating rat pituitary cells, i t is suggested that the coupling of the CRF-R1 to intracellular signal ing in Leydig cells is different from that in corticotropic pituitary cells, at least in quantitative terms.