Myocardial adenosine salvage rates and restoration of ATP content following ischemia

Abstract

The isolated perfused rat heart was utilized to determine the maximum rate of adenosine incorporation into adenine nucleotides and the effect of ischemia on this rate. In aerobic hearts, the rates of [8-14C]adenosine incorporation into nucleotides in nanomoles/minute per gram dry tissue were ATP 34 +/- 2, ADP 6 +/- 0.4, AMP 3 +/- 0.3, and IMP, 1 +/- 0.2. Following ischemia these values were not significantly different except for the rate of incorporation into IMP, which doubled. The extent of adenosine deamination with one pass through the coronary vasculature was the same in aerobic and postischemic hearts: 2% and 7% of the perfusate adenosine was converted to hypoxanthine and inosine, respectively. These percentages were similar at 50, 100, and 200 micron adenosine. Perfusion of aerobic hearts for 5 h with adenosine did not change ATP concentrations. Therefore, [8-14C]adenosine incorporation into ATP in these hearts appeared to represent ATP turnover. In contrast, 5 h perfusion of postischemic hearts with adenosine restored ATP concentrations to control values. The synthesis rate calculated from the increase in ATP concentration was comparable to the synthesis rate calculated from [8-14C]adenosine incorporation. Thus, incorporation of [8-14C]adenosine into ATP in postischemic hearts represented net ATP synthesis.