NITRIC-OXIDE PRODUCTION BY CULTURED RAT LEYDIG-CELLS

Nitric oxide (NO) has emerged as an intracellular and intercellular me ssenger in a number of biological systems. Ln the present study, we de monstrated that NO was produced by cultured rat Leydig cells, and that inducible nitric oxide synthase (iNOS) messenger RNA (mRNA) was expre ssed in Leydig cells. NO was measured as nitrite with the method of Gr iess. Although unstimulated Leydig cells produce little NO, interleuki n-1 beta (IL-1 beta) markedly increased NO production. NO production w as inhibited by the NOS inhibitor, N-G-monomethyl-L-arginine. Northern blot analysis showed that iNOS mRNA was little expressed in freshly i solated immature Leydig cells, but that iNOS mRNA levels were increase d by the addition of IL-1 beta in a dose-dependent manner at the conce ntration up to 10 ng/ml. The levels of iNOS mRNA were increased as ear ly as 3 h after the addition of IL-1 beta and persisted for up to 24 h . In adult Leydig cells, IL-1 beta stimulated iNOS mRNA expression. Im munocytochemical analysis demonstrated iNOS-like immunoreactivity in t he cytoplasm of Leydig cells. These results indicate that NO is produc ed in Leydig cells and suggest that NO might be involved in the physio logical function of Leydig cells.