In vitro/in vivo effects of ethane dimethanesulfonate on Leydig cells of adult rats.

Although ethane dimethanesulfonate (EDS) is well recognized as a Leydig cell toxicant, the dose responsiveness of Leydig cells to EDS, both in vitro and in vivo, is not well established. In addition, the cellular site of action of EDS during Leydig cell toxicity and the status of Leydig cell viability during the affected period remain controversial. We determined the in vitro EC50 (370 microM) and in vivo ED50 (60 mg/kg) for human chorionic gonadotropin (hCG)-stimulated testosterone (T) production using both highly purified (98%) and interstitial (14%) Leydig cell preparations, respectively. Leydig cells were recovered in approximately equal numbers following all in vivo and in vitro EDS exposures. The Leydig cells in these preparations were viable and steroidogenically active (3 beta-HSD positive) subsequent to all exposures, both before and after incubations to stimulate T biosynthesis. When hCG-stimulated T production was decreased 50% following in vivo or in vitro exposures, the morphological integrity of the Leydig cells appeared normal, with no discernible lesion at either the light or the electron microscope level. We used stimulants of various reactions in the pathway of T biosynthesis (20 alpha-hydroxycholesterol and pregnenolone) to determine the site of action impaired when T biosynthesis was decreased. Our results indicate that when Leydig cells are exposed to EDS either in vitro or in vivo, the biosynthesis of T is compromised between the cyclic adenosine monophosphate activation of protein kinase and the cholesterol side chain cleavage enzyme.