[Cyclic AMP level, dissociation of membrane-bound calmodulin and regulation of calcium transport in the heart sarcoplasmatic reticulum in circulatory hypoxia].

Slight alterations in calmodulin-stimulated and distinct alterations in cAMP-dependent regulation of calcium transport were found in dog heart microsomes under conditions of circulatory hypoxia as compared with myocardium of healthy animals. After addition into the incubation mixture of exogenous protein kinase simultaneously with calmodulin and cAMP the rate of 45Ca accumulation became similar both in microsomes of intact and impaired myocardium. In the hypoxia membrane-bound calmodulin was dissociated in cardiomyocytes and its content was increased in cytosol, whereas content of cAMP tended to decrease; under these conditions activity of Ca2+-ATPase in sarcoplasmic reticulum was similar to the control values.