The role of calcium ions in the control of myocardial mechanical performance and oxygen consumption by coronary perfusion pressure.
The effect of changes in extracellular Cap2+ concentration (Cp2+) (0.65-5.2 mM) on increases of left ventricular mechanical performance and O2 consumption (MVO2) induced by the elevation perfusion pressure (PP) was studied in closed and drained ventricle isolated rat heart preparation perfused by the modified Langendorff technique. Coronary flow and left ventricular systolic pressure did not depend on Cap2+. In contrast, elevation of Cap2+ potentiated the rise of dp/dtmax considerably. Thebesius flow was significantly lower at high Cap2+ levels. The initial phase of the MVO2 increase in the low PP range (20-60 mmHg) was not influenced by changes in Cap2+. At higher PP levels (80-160 mmHg) elevation of Ca2p+ significantly potentiated the MVO2 increase in the closed ventricle preparation, and if the slowly rising phase of MvO2 increase induced by the elevation of PP was eliminated by draining the left ventricle, the magnitude of the plateau phase of MVO2-PP relationship was a function of Cap2+. Hypoperfusion at the lowest PP level (20 mmHg) (coronary flow was always less than 2 ml/min) caused significant impairment of mechanical activity and MVO2, which could not be compensated for by elevation of Cap2+.
D000818:Animals; D001794:Blood Pressure; D002118:Calcium / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects*; D010477:Perfusion; D011312:Pressure; D051381:Rats; D012039:Regional Blood Flow
D002118:Calcium