Relationship of pyruvate and lactate during anaerobic metabolism. V: Coronary adequacy

Veno-arterial differences of pyruvate and lactate across the myocardium in chloralose-anesthetized dogs were very variable; in any one animal they changed continually with time despite constant blood flow and arterial blood concentrations. There was a systematic tendency of v-a lactate to vary with v-a pyruvate, as expressed in the calculated "Δ excess lactate," which remained nearly constant (or, if blood flow changed, bore a constant ratio to (a-v)O 2 ). No change in Δ excess lactate from control values occurred in nonhypoxic experiments despite marked changes in v-a differences, arterial blood composition, and coronary flow. Cardiac Δ excess lactate became positive in most animals breathing 10% O 2 in N 2 ; output of excess lactate was also observed in all those in which moderate muscular exercise was induced. This anaerobic metabolism, or change in the relationship between pyruvate and lactate exchanges, was interpreted as an indication that O 2 delivery response was not adequate to meet cardiac tissue requirements during such mild stresses when judged by the standards of adequacy of the basal state.