Effects of Luteinizing Hormone and Insulin on the Regulation of Prolactin Receptors in Leydig Cells of Adult Rat

Effects of luteinizing hormone (LH), insulin and their combination on the regulation of prolactin (PRL) receptors on Leydig cells were studied. Leydig cells were isolated from adult male Wistar rats and measurement of PRL binding and internalization was done by incubating the cells with saturating concentration of ¹²⁵I-PRL in the presence or absence of different doses of unlabeled LH/ insulin. LH exposure caused biphasic pattern of changes in Leydig cells surface binding of ¹²⁵I-PRL was increased only by 100 and 200 ng doses of LH. Exposure of insulin at all doses registered no significant change in both cell surface bound and internalized PRL receptors. In normal cells, surface binding of ¹²⁵I-PRL was greater than the internalization at 34°C but at 4°C, surface binding remained lower than that at 34°C with negligible internalization.