Rates of glucose and lactate oxidation by the perfused isolated trout (Salvelinus fontinalis) heart

Abstract

Isolated brook trout (Salvelinus fontinalis) hearts were perfused with buffer containing either [U-¹⁴C]glucose or [U-¹⁴C]lactate and the rate of ¹⁴CO₂ production monitored. Lactate oxidation rates were higher than glucose oxidation rates when either substrate was provided individually. When glucose and lactate were offered simultaneously glucose oxidation was markedly inhibited whereas there was only a minor inhibitory effect upon lactate oxidation. It appears that the fish heart preferentially utilizes lactate as a metabolic fuel under aerobic conditions.