Differences in response to activation of adenylyl cyclase by various stimulants in human myocardium.

The response of adenylyl cyclase complex in human atrial tissue removed at corrective surgery of normoxemic and hypoxemic congenital heart defects in children to various stimulants was evaluated and related to the oxygenation state of the myocardium. When comparing response to stimulation in normoxemic and hypoxemic atria a higher basal as well as stimulated adenylyl cyclase activity was found in hypoxemic atria; an insignificant stimulatory effect of isoprenaline in normoxemic hearts became significant in the atria of hypoxemic patients. Hypoxemic samples also showed two times higher activity when the total catalytic activity was evaluated by the stimulation with forskolin. Higher stimulatory effect of Gpp/NH/p was also observed in hypoxemic than in normoxemic state. Increased adenylyl cyclase activity might represent one of adaptive mechanisms to hypoxemia in patients with congenital heart defects.