Calcium, strontium, and barium movements during ischemia and reperfusion in rabbit ventricle. Implications for myocardial preservation.

Abstract

Global ischemia was induced in isolated blood-perfused rabbit interventricular septa at 37.degree. C beating at 72 beats/min. Uptake of 133BaCl2 (0.85 .mu.M) or 85SrCl2 (0.4 .mu.M) during perfusion with solutions containing 2.5 mM CaCl2 was monitored by .gamma. probe. Since Ba is not sequestered by sarcoplasmic reticulum, its uptake was used to monitor sarcolemmal function. The uptake of 133BaCl2 increased from 21.1 .+-. 5.5 to 29.5 .+-. 8.2 pmol/min (P < 0.05) upon reperfusion after 30 min of ischemia and from 13 .+-. 2.9 to 28.5 .+-. 5.7 pmol/min (P < 0.05) after 60 min of ischemia. There was no change in 85Sr uptake until reperfusion after 60 min of ischemia when it increased from 8.5 .+-. 1.8 to 29.3 .+-. 11.4 pmol/min (P < 0.025). The effects of Ca upon recovery were assessed. Ten septa made ischemic for 60 min and reperfused with 1.5 mM CaCl2 recovered 31.6 .+-. 9.1% of preischemia developed tension. Ten other septa reperfused with red cell perfusate containing 0.75 mM CaCl2 for 5 min, then exposed to red cell perfusate containing 1.5 mM CaCl2 recovered 67.1 .+-. 7.5% (P < 0.05) of preischemia developed tension. Improved recovery was shown after 20 min of ischemia, 77.4 .+-. 6.1% vs. 103.4 .+-. 7.8% (P < 0.025). Five septa reperfused with anoxic Tyrode''s solution containing 50 .mu.M CaCl2 after 15 min and 45 min of total ischemia showed no decrease in resting tension despite a progressive rise during ischemia. Resting tension upon reperfusion with red cell perfusate depended strongly upon perfusate Ca concentration. Impaired relaxation during ischemia had Ca-dependent and Ca-independent components. A mild sarcolemmal leak of 133Ba after 30 min progressed to severe disruption after 60 min of ischemia. Reperfusion with red cell perfusate containing 0.75 mM CaCl2 for 5 min enhanced recovery. Ischemic injury can be significantly modified by the Ca content of the blood with which the myocardium is reperfused.