[Cyclic GMP- and AMP-modified calcium binding by the myocardial sarcolemma in circulatory hypoxia]

10(-6) M cAMP were shown to induce a 61% and 21% increase in 45Ca binding to sarcolemma proteins in intact and injured (circulatory hypoxia) hearts, respectively. The addition of exogenous protein kinase equalized 45Ca-binding levels in normal and impaired sarcolemma. The decrease in 45Ca-binding capacity by 16 and 36% was detected in the presence of 10(-7) and 10(-6) M of cGMP, respectively. In impaired hearts, cAMP and Ca-ATPase activity levels remain constant, while cGMP content increases, as compared to normal myocardial level.