Exogenous GTP Enhances the Effects of Sodium Nitrite on Cyclic GMP Accumulation, Vascular Smooth Muscle Relaxation and Platelet Aggregation

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Abstract
Exogenous guanosine triphosphate (GTP) (1-2 x 10(-4)M) resulted in increased concentrations of cyclic GMP both in endothelium denuded rat mesenteric artery (RMA) and in human ADP-stimulated platelets. Sodium nitrite (3.3 x 10(-4)M) relaxed precontracted RMA by 34%. When the arteries were preincubated with GTP (2 x 10(-4)M) sodium nitrite administration resulted in a significantly greater relaxation (58%) of the RMA with concomitant 2-fold increase in cGMP. Sodium nitrite (1 x 10(-4)M) had an inhibitory effect on ADP-induced platelet aggregation. Preincubation with GTP enhanced significantly the sodium nitrite-induced inhibition of ADP-induced platelet aggregation with a simultaneous 5-fold increase in cGMP. These results indicate that exogenous GTP enhances the sodium nitrite-induced stimulation of guanylate cyclase and thus enhances the effects of sodium nitrite on arterial smooth muscle and platelets.