Effects of propionate on mechanical and metabolic performance in aerobic rat hearts.

The purpose of this report is to describe the contribution of propionate as an adjunct source of oxidative metabolism in aerobic myocardium. In the first series of studies, six groups of isolated working rat hearts (n = 6-8 per group) were perfused for 40 minutes with Krebs-Henseleit media containing 11 mM glucose. Propionate treatment was provided to the media at a constant dose per heart group and extended over a range of dosages, including: 0 (placebo control), 0.1, 0.5, 1.0, 5.0, and 10.0 mM, buffered to pH 7.4. Average aerobic coronary blood flow for all groups was 21.5 +/- 0.6 ml/min; average left ventricular peak systolic pressure was 123.7 +/- 1.4 mmHg. There were no significant differences among groups compared with placebo hearts for aortic flow, heart rate x aortic pressure product, or myocardial oxygen consumption, although performance tended to decline in the 10 mM group. A clear dose-response relationship was observed in 14CO2 production from labeled propionate, with a 12-fold increase between the 0.1 and 10 mM groups. Most of the increase occurred at the lower dosages, with a relative leveling off at the 1.0, 5.0, and 10.0 mM doses. In part 2, propionate was examined as a sole substrate. At 1.0 mM without glucose, propionate per se was unable to support mechanical function over the course of the perfusions, but still maintained high rates of oxidation, comparable to that of the 1.0 mM group with glucose in part 1.(ABSTRACT TRUNCATED AT 250 WORDS)