Comparison of the positive inotropic effects of serotonin, histamine, angiotensin II, endothelin and isoprenaline in the isolated human right atrium

Publisher Website
Google Scholar
Abstract
Summary The receptor systems through which serotonin (5-HT), histamine, angiotensin II and endothelin increase the force of contraction were studied in isolated right atria from patients without apparent heart failure. All agonists increased the atrial force of contraction in a concentration-dependent manner; maximal effects, however, were significantly less than those evoked by isoprenaline or Ca2+. 5-HT and histamine, but not angiotensin II and endothelin, activated adenylate cyclase, whereas endothelin and angiotensin II stimulated inositol phosphate generation. Experiments with subtype-selective antagonists revealed that histamine effects were mediated by H2-receptors (sensitive to ranitidine), 5-HT-effects by 5-HT4-receptors (sensitive to SDZ 205-557) and angiotensin II effects by AT1-receptors (sensitive to losartan). We conclude that in human right atria the force of contraction can be increased by cyclic AMP-dependent (histamine, 5-HT) and -independent (angiotensin II, endothelin) pathways. Compared to β-adrenoceptors, however, all other receptor systems increase the force of contraction only submaximally indicating that the β-adrenoceptor pathway is the most important physiological mechanism to regulate force of contraction and/or heart rate in the human heart.

This publication has 39 references indexed in Scilit: