Leydig Cell Cooperation In Vitro: Evidence for Communication Between Adult Rat Leydig Cells

Abstract

In short‐term incubations (32 C, 3 h) of purified adult rat Leydig cells, increasing the density from 5000 to 50,000 cells/16 mm diameter culture well caused a significant increase in human chorionic gonadotropin (hCG)‐stimulated testosterone secretion/cell. Density‐dependent stimulation was also observed under basal conditions and in the presence of dibutyryl cyclic adenosine monophosphate, luteinizing hormone‐releasing hormone, or 22‐hydroxy cholesterol. In contrast, increasing the incubation density of purified Leydig cells by addition of other testicular cells had no effect on basal or hCG‐stimulated testosterone secretion. hCG‐stimulated testosterone secretion by Leydig cells incubated at low density was also increased by addition of Leydig cell‐conditioned medium. This stimulatory activity was removed by charcoal extraction and by ultrafiltration (approximately 30 kDa cut‐off). The data indicate that Leydig cells cooperate by secretion of low molecular weight, cell‐specific stimulatory factors that support Leydig cell steroidogenesis in vitro, and may also play a role in regulating Leydig cell function in vivo.