SERTOLI CELLS AS POTENTIAL TARGETS OF PROLACTIN ACTION IN THE TESTIS

Using primary cultures of porcine Sertoli cells as a model, the effect s of ovine prolactin (oPRL) on Sertoli cell function were investigated through FSH binding. PRL treatment (0.3-5 ng/ml) induced a dose-depen dent increase (ED(50) = 5.10(-11) M) of I-125-FSH binding to Sertoli c ells to a maximal stimulation (about 2.5-fold increase). This effect w as time-dependent, being detected within 2 h (P < 0.02) after oPRL tre atment and was maximal after 24 h. The effect of oPRL is probably medi ated via specific PRL receptors identified by different approaches suc h as immunohistochemistry, binding assays and cross-linking experiment s. Immunohistochemical experiments were performed using two antibodies directed against the PRL receptor. Immunoreactivity was detected both in the Sertoli cell cytoplasm and in the perinuclear area. Scatchard plots of binding studies revealed the presence of specific binding sit es for PRL both in the Sertoli cell membranes and nuclear fractions wi th high affinity constants (K-d = 0.8 and 1.4 nM, respectively). Affin ity labeling of these receptors by covalently binding to I-125-oPRL an d subsequent electrophoretic analysis of the labeled complexes reveale d for the cell membranes, two major labeled bands of 74 and 64 kDa and three other faintly labeled bands of 190, 150 and 140 kDa. For the nu clear fractions, three major labeled bands with high molecular weights of 190, 150 and 140 kDa were observed. Taken together, the present fi ndings suggest that Sertoli cells are potential targets for prolactin action in the porcine testis.