The purpose of this study was to investigate the effects of NO on cytosolic calcium levels in Balb/c 3T3 fibroblasts that were previously shown to lack soluble guanylate cyclase activity. Authentic NO as well as two NO-generating vasodilators, S-nitroso-N-acetyl-penicillamine and isosorbide dinitrate, decreased cytosolic calcium in these fibroblasts. The effect of NO and S-nitroso-N-acetylpenicillamine was concentration-dependent and, for the most part, reversible. Since

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... llamine did not increase either cGMP or cAMP, NO did not increase cGMP, and 8-bromo-cGMP did not alter cytosolic free calcium, we conclude that NO decreases cytosolic free calcium by a cyclic nucleotide-independent mechanism in Balb/c 3T3 fibroblasts.