EFFECTS OF DIFFERENT OXIDATIVE INSULTS ON INTERMEDIARY METABOLISM IN ISOLATED-PERFUSED RAT HEARTS

C-13 and P-31 NMR were used to evaluate exogenous substrate utilizatio n and endogenous phosphate metabolites in perfused rat hearts exposed to tert-butylhydroperoxide (tert-BOOH) and hydrogen peroxide (H2O2). B oth reagents caused a reduction in developed pressure compared to cont rols and, in agreement with previous P-31 NMR data,(8) had different e ffects on intracellular high-energy phosphates and glycolysis. C-13 Is otopomer analysis of tissue extracts showed that H2O2 and tert-BOOH al so had significantly different effects on substrate utilization by the citric acid cycle. The contribution of exogenous lactate and glucose to acetyl-CoA was 43% in controls and increased to over 80% in the pre sence of either oxidant. With tert-BOOH, exogenous glucose and lactate were both significant contributors to acetyl-CoA (44 +/- 2 and 41 +/- 3%). However, with H2O2, exogenous lactate supplied a much higher fra ction of acetyl-CoA (72 +/- 2%) than glucose (9 +/- 1%). Also, when [2 -C-13]glucose was supplied, accumulation of [2-C-13] and [5-C-13]fruct ose 1,6-bisphosphate was observed in the presence of H2O2, indicating inhibition of glyceraldehyde-3-phosphate dehydrogenase. These results indicate that despite this glycolytic inhibition, H2O2 increased the u tilization of pyruvate precursors when lactate was present as an alter native carbohydrate substrate.