DIFFERENCES IN RESPONSE TO ACTIVATION OF ADENYLYL-CYCLASE BY VARIOUS STIMULANTS IN HUMAN MYOCARDIUM

The response of adenylyl cyclase complex in human atrial tissue remove d at corrective surgery of normoxemic and hypoxemic congenital heart d efects in children to various stimulants was evaluated and related to the oxygenation state of the myocardium. When comparing response to st imulation 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 sampl es also showed two times higher activity when the total catalytic acti vity was evaluated by the stimulation with forskolin. Higher stimulato ry effect of Gpp/NH/p was also observed in hypoxemic than in normoxemi c state. Increased adenylyl cyclase activity might represent one of ad aptive mechanisms to hypoxemia in patients with congenital heart defec ts.