Effects of perfusion pressure on intracellular calcium, energetics, and function in perfused rat hearts.
Effects of perfusion pressure in a range from 50 to 140 cmH2O on intracellular Ca2+ concentration ([Ca2+]i) were evaluated along with cardiac function, energy metabolism, and left ventricular geometry in a concentration of 2 or 4 mM of extracellular Ca2+ ([Ca2+]o) in isovolumic perfused rat hearts. [Ca2+]i was evaluated with a surface fluorometry technique in hearts loaded with indo-1/AM. The systolic and diastolic values and the amplitude (difference between systolic and diastolic values) of indo-1 fluorescence ratio (an index of [Ca2+]i) were linearly related to perfusion pressure. Changes in the fluorescence ratio were harmonious with rapid changes in left ventricular pressure and stabilized within 30-40 s after changes in perfusion pressure. Developed pressure and O2 consumption were closely, linearly correlated with the fluorescence ratio irrespective of [Ca2+]o. Left ventricular end-diastolic wall thickness, measured by 2-dimensional echocardiography, paralleled perfusion pressure and showed a good correlation with the fluorescence ratio. Diastolic myocardial adenosine 3',5'-cyclic monophosphate significantly decreased only at the lowest perfusion pressure. The ln[phosphocreatine]/[Pi] also changed with altered perfusion pressure. In conclusion, perfusion pressure modulates [Ca2+]i, which in turn regulates myocardial contraction and associated O2 utilization.
Kojima
S
S
Department of Medicine, University of California, San Francisco 94143.
Wu
S T
ST
Watters
T A
TA
Parmley
W W
WW
Wikman-Coffelt
J
J
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003326:Coronary Circulation / Q000502:physiology*; D004734:Energy Metabolism; D005456:Fluorescent Dyes; D005470:Fluorometry; D006321:Heart / Q000502:physiology*; D066298:In Vitro Techniques; D007211:Indoles; D007425:Intracellular Membranes / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D011312:Pressure; D051381:Rats; D011921:Rats, Inbred WKY
D005456:Fluorescent Dyes; D007211:Indoles; C048960:indo-1; D002118:Calcium