Glyceryl trinitrate increases platelet cyclic GMP after metabolism in fibroblasts

Glyceryl trinitrate had no direct effect on cyclic GMP levels in platelets. However, in the presence of fibroblasts (RFL-6 cells), glyceryl trinitrate increased platelet cyclic GMP up to 7.8 fold (11.5 fold in the presence of superoxide dismutase). Fibroblasts alone had no effect. Endothelial cells alone increased platelet cyclic GMP up to 4.1 fold (9.6 fold in the presence of superoxide dismutase), but glyceryl trinitrate had no additional effect. Thus fibroblasts, but not endothelial cells, metabolize glyceryl trinitrate to a nitric oxide-like material that stimulates platelet soluble guanylyl cyclase.