Cyclic GMP stimulation by vasopressin in LLC-PK1 kidney epithelial cells is L-arginine-dependent.

The L-arginine antagonist NG-monomethyl-L-arginine has been shown to inhibit nitric oxide formation from L-arginine in endothelial cells. In the present study NG-monomethyl-L-arginine was used to assess the role of L-arginine for cyclic GMP stimulation by vasopressin in a kidney epithelial cell line (LLC-PK1). Preincubation of cells with 1 mumol/l, 10 mumol/l and 100 mumol/l NG-monomethyl-L-arginine decreased cyclic GMP stimulation at 1 mumol/l vasopressin by 25%, 71% and 90%, respectively. This inhibition by NG-monomethyl-L-arginine was markedly reduced by L-arginine (2 mmol/l) but not D-arginine (2 mmol/l). Cyclic GMP stimulation by the calcium ionophore A23187 was also inhibited by NG-monomethyl-L-arginine and enantioselectively restored by L-arginine. However, NG-monomethyl-L-arginine did not affect cyclic GMP stimulation by sodium nitroprusside that spontaneously releases nitric oxide. These results suggest that, in kidney epithelial cells, vasopressin induces nitric oxide formation from L-arginine leading to activation of soluble guanylate cyclase. It is concluded that nitric oxide formation from L-arginine is not only responsible for endothelium-dependent relaxation but may be a more general pathway with regulatory function for intracellular guanylate cyclase activity.