Effect of elevated lactataemia on the rates of lactate turnover and oxidation in rats.

Abstract

1 The L-Lactate14C(U) priming dose-perfusion technique was used to measure the rates of lactate turnover and oxidation in anesthetized and mechanically ventilated rats. Lactataemia ([L]) was normal (0.5–1mM) or elevated either through moderate hypoxaemia or after lactate loading in normoxic conditions. 2. Lactate turnover and oxidation rates increased linearly with [L] up to 6 mM and the values of the three groups stand on same lines. 3. The slope of the regression line of oxidation rate vs [L] was lower than the turnover one. Thus an increasing part of the lactate flow was oriented to other metabolic pathways in these hyperlactataemic conditions. 4. 15% of the metabolic rate was explained by lactate oxidation in basal condition (50% of the turnover rate oxidized). This participation of [L] to the total energy expenditure increased when [L] rose and reached 45% when [L] is 6 mM. 5. These results are discussed in the light of the physiological role of lactate as metabolic regulator, glucose precursor and energetic substrate.