Demonstration of a high affinity component of glyceryl trinitrate induced vasodilatation in the bovine mesenteric artery.

Strips of bovine mesenteric artery mounted in disposable organ baths made of polyethylene showed a biphasic relaxation pattern when exposed to glyceryl trinitrate (GTN). The concentration response curve could be resolved into a high affinity component (pD2 11.9) and a low affinity component (pD2 7.5) by means of non-linear regression analysis. The relaxation induced by both low (0.01 nM - 0.1 nM) and high (1 microM) concentrations of GTN seemed to be mediated by cyclic GMP. We found a 2-3-fold increase in cGMP at 0.01 - 0.1 nM GTN and a 5-fold increase at 1 microM GTN. Cyclic AMP levels were unchanged. We also found that GTN-induced relaxation was increased, for a given GTN concentration, when the endothelium was removed, especially in the low concentration range.