Metabolic adjustments to diving and recovery in the African lungfish

The metabolic potentials of the heart, brain, white muscle, and liver in the African lungfish were estimated by enzymatic data. Metabolic effects of a 12-h submergence were monitored using metabolite measurements. Heart was the most oxidative tissue but also showed the greatest anaerobic potential. The brain displayed relatively low oxidative capabilities. White muscle remained almost inert. Although high-energy phosphate concentrations in brain and heart did not fall during submergence, glycolysis was activated as indicated by crossover plots, depletion of endogenous glycogen stores, and lactate accumulation. Blood-tissue lactate and glucose gradients indicated 1) that the heart and brain released lactate throughout submergence, 2) that after 12 h of submersion the brain and heart were probably obtaining all their required glucose from the blood, 3) that the liver released glucose throughout submergence, and 4) that white muscle was metabolically isolated from the rest of the body during submergence. It appeared that perfusion adjustments occurring during submergence were directed more toward regulating intertissue exchange of metabolites than toward oxygen conservation. Comparisons are made to diving responses in mammals.