Nutritional Circulation in the Heart: IV. Effect of Calcium Chloride and Potassium Chloride on Myocardial Hemodynamics and Clearance of 86Rubidium

The effect of a constant intracoronary infusion of potassium chloride and calcium chloride upon myocardial hemodynamics and clearance of 86Rubidium in the heart was studied in the isolated supported dog heart preparation (ISHP). In the ISHP with a constant coronary blood flow, potassium chloride in doses up to 4mg/min had no significant effect upon either the myocardial hemodynamics (MH), clearance of 86Rubidium (C86Rb) or the capillary transport coefficient, PS. Calcium chloride in small doses had no effect upon the MH, C86Rb or PS. A higher dose of calcium chloride (4mg/min) produced an increase in myocardial contractile force, left ventricular peak systolic pressure, myocardial oxygen consumption and a decrease in C86Rb and PS. Pretreatment of the ISHP with practolol (0.25mg/Kg), an agent which blocks adrenergic β-receptors, did not modify the effects of calcium chloride upon the MH, C86Rb or PS. It is concluded that the effects of calcium chloride are exerted directly, independent of a β-receptor mediation.