Effects of cysteine and nitroglycerin on bovine heart guanylate cyclase and on tissue cyclic GMP and lactate of rat atria.

The effects of thiols on guanylate cyclase activation by nitroglycerin were studied in bovine heart and the effects of cysteinee and nitroglycerin on the tissue levels of cyclic GMP and lactate were studied in beating rat atria. Cysteine (2.5 X 10(-3) M) together with nitroglycerin (1 X 10(-3) M), increased 15-fold the activity of guanylate cyclase. In hypoxia, nitroglycerin (1 X 10(-3) M) together with cystein (5 X 10(-3) M) increased cyclic GMP and decreased the tissue lactate level. It is concluded that cysteine potentiates the effect of nitroglycerin on cyclic GMP formation even in integrated cell systems with an intact physiological function.