Effects of L-arginine in rat adrenal cells: Involvement of nitric oxide synthases

The effects of L-arginine on corticosterone production, cGMP, and nitrite l evels were examined in zona fasciculata adrenal cells. L-Arginine significa ntly decreased both basal and ACTH-stimulated corticosterone production. Th is effect was still evident when steroidogenesis was induced by 8-bromo-cAM P and 22(R)-hydroxycholesterol, but not in the presence of exogenously adde d pregnenolone. L-Arginine increased cGMP and nitrite levels,; these effect s were blocked by the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl-ester. Transport of L-[H-3]arginine was rapid, saturable, and monoph asic, with an apparent K-m of 163 +/- 14 mu M and a maximum velocity of 53 +/- 6 pmol/min 10(5) cells. The basic amino acids L-lysine and L-ornithine, but not D-arginine or the nitric oxide synthase inhibitors NG-nitro-L-argi nine methyl-ester and NG-nitro-L-arginine, impaired L-arginine uptake. Take n together, these results suggest that steroidogenesis in tons fasciculata adrenal cells may be negatively modulated by L-arginine-derived nitric oxid e.