FUNCTIONAL-SIGNIFICANCE OF ANGIOTENSIN RECEPTORS IN HUMAN MYOCARDIUM - SIGNIFICANT DIFFERENCES BETWEEN ATRIAL AND VENTRICULAR MYOCARDIUM

We studied the effects of angiotensin (Ang) I and II in a variety of i solated human cardiac tissues contracting under physiological conditio ns (37 degrees C, 60 beats.min(-1)). Ang I and II consistently increas ed the peak developed force of human atrial muscles by 30-40%, an effe ct that was completely blocked by 10(-6) M saralasine, but not by the combination of prazosin and propranolol. However, neither Ang I or II had significant inotropic effects in right and left ventricular human preparations. We were also able to demonstrate that the positive inotr opic effect of Ang II in human right atrial tissue is mediated by the ATI receptor subtype but not the AT(2) receptor subtype.