Oxidation of Lactate to Carbon Dioxide by Rainbow Trout (Salmo gairdneri) Tissues

Abstract

A comparative study on the ability of various fish tissues to carry out different stages of lactate oxidation was conducted with rainbow trout (Salmo gairdneri). Rate of oxidation of Na-L-lactate-1-14C (5 mM) and Na-L-lactate-3-14C (5 mM) by tissue slices from white muscle, red lateral line muscle, heart, liver, kidney, and gills was determined at 15 C by measuring the formation of 14CO2. In all tissues the liberation of 14CO2 was considerably higher with lactate-1-14C than with lactate-3-14C. Liver was the most active tissue for oxidation of lactate-1-14C (2805 mμmoles/g wet tissue/hr at 15 C) and gills for oxidation of lactate-3-14C (556 mμmoles/g wet tissue/hr at 15 C). With both substrates activity in the white muscle was very limited, whereas other tissues had an intermediate level of activity. The results suggest that, in trout, the catabolism of lactate may take place through oxidative decarboxylation of pyruvate and that liver plays an important role in such a process. It appears also that complete oxidation of lactate may be of significance in supplying energy for the exchange reactions in gills.