30 Effects of angiotensin II on cytosolic calcium releases in isolated ventricular myocytes from adult normal and hypertensive rats

METHODS:This study investigated the effects of angiotensin II (Ang II; 10-10mol/l) on calcium releases in ventricular myocytes from normal and renal hypertensive adult rats (Goldblatt two kidney one clip). Newly isolated myocytes were loaded with fluorescent indo-1/AM and studied at rest or under electrical stimulation. The variation of the ratio of indo-1 emission (405/480 nm) was taken as a measure of cytosolic calcium variation. Five parameters were investigated from each peak systolic indo-1 ratio before and after Ang II additionamplitude variation, duration with analysis of a rise time and a fall time, and frequency of spontaneous calcium releases. RESULTS:The following changes were observed(1) in unstimulated myocytes exhibiting spontaneous contractile activity, an increase in the frequency of calcium transients, at 10mol/l, in normal cells (+157±27%, P