N-Hydroxylamine is not an intermediate in the conversion of L-arginine to an activator of soluble guanylate cyclase in neuroblastoma N1E-115 cells

This study evaluates the role of N-hydroxylamine (NH₂OH) in activating soluble guanylate cyclase in the mouse neuroblastoma clone N1E-115. It has been proposed that NH₂OH is a putative intermediate in the biochemical pathway for the generation of nitric oxide (NO)/endothelium-derived relaxing factor (EDRF) from L-arginine. NH₂OH caused a time- and concentration-dependent increase in cyclic GMP formation in intact cells. This response was not dependent on Ca²⁺. In cytosol preparations the activation of guanylate cyclase by L-arginine was dose-dependent and required Ca²⁺ and NADPH. In contrast, NH₂OH itself did not activate cytosolic guanylate cyclase but it inhibited the basal activity of this enzyme in a concentration-dependent manner. The formation of cyclic GMP in the cytosolic fractions in response to NH₂OH required the addition of catalase and H₂O₂. On the other hand, catalase and/or H₂O₂ lead to a decrease in L-arginine-induced cyclic GMP formation. Furthermore, NH₂OH inhibited L-arginine- and sodium nitroprusside-induced cyclic GMP formation in the cytosol. The inhibition of L-arginine-induced cyclic GMP formation in the cytosol by NH₂OH was not reversed by the addition of superoxide dismutase. These data strongly suggest that NH₂OH is not a putative intermediate in the metabolism of L-arginine to an activator of guanylate cyclase.