STIMULATION OF CYCLIC-GMP PRODUCTION IN CULTURED ENDOTHELIAL-CELLS OF THE PIG BY BRADYKININ, ADENOSINE-DIPHOSPHATE, CALCIUM IONOPHORE A23187 AND NITRIC-OXIDE

1. The effects of bradykinin, adenosine diphosphate, calcium ionophore A23187 and nitric oxide on the production of adenosine 3':5'-cyclic monophosphate (cyclic AMP) and guanosine 3':5'-cyclic monophosphate (cyclic GMP) were investigated in cultured aortic endothelial cells of the pig. 2. Bradykinin (10-7 M), adenosine diphosphate (3 x 10-5 M), nitric oxide (2 x 10-6 M) and A23187 (10-6 M) stimulated the production of cyclic GMP. This stimulation reached a maximum within 1 min and declined rapidly with the first three agonists whereas that induced by A23187 was long-lasting. 3. These concentrations of bradykinin, A23187 and nitric oxide had no effect on cyclic AMP production. However, adenosine diphosphate (3 x 10-5 M) slightly but significantly enhanced its production by about 1.7 fold. 4. The basal content of cyclic GMP in endothelial cells was significantly reduced by haemoglobin (10-5 M, a scavenger of endothelium-derived relaxing factor(s)) and methylene blue (10-5 M, and inhibitor of the activation of soluble guanylate cyclase) and was significantly enhanced by superoxide dismutase (500 u ml-1, a scavenger of superoxide anions). The basal content of cyclic GMP was not affected by N(G)-monomethyl-L-arginine (10-5 M, a specific inhibitor of the formation of nitric oxide from L-arginine) and was slightly but significantly increased by its D-enantiomer, N(G)-monomethyl-D-arginine. 5. The production of cyclic GMP stimulated by bradykinin, adenosine diphosphate, A23187 and nitric oxide was inhibited by haemoglobin (10-5 M) and methylene blue (10-5 M) but was unaffected by superoxide dismutase (500 u ml-1). 6. The production of cyclic GMP stimulated by bradykinin, adenosine diphosphate or A23187, but not that stimulated by nitric oxide, was significantly reduced by N(G)-monomethyl-L-arginine (10-5 M). The production of cyclic GMP evoked by nitric oxide, but not that induced by the other three agents, was enhanced significantly by N(G)-monomethyl-D-arginine by about 1.5 fold. 7. These data indicate that the endothelium-dependent vasodilators bradykinin, adenosine diphosphate and A23187 activate the production of cyclic GMP in endothelial cells via the synthesis of nitric oxide, which in turn stimulates the soluble guanylate cyclase.