Reversible metabolic depression in hepatocytes of lamprey (Lampetra fluviatilis) during pre-spawning: regulation by substrate availability

The regulation of oxidative metabolism in hepatocytes of lampreys (Lampetra fluviatilis) during the freshwater pre-spawning period of their life cycle was studied. The energy metabolism in these cells is characterized by a si mplified scheme. where glycolytic ATP production is insignificant and fatty acids are the major respiratory substrates. Seasonal changes in aerobic ce ll metabolism include a considerable reversible depression of metabolic rat e in lamprey hepatocytes during the winter months of the pre-spawning perio d. The depression is characterized by a more than twofold decrease in hepat ocyte endogenous respiration rate, a reduction of oxidative phosphorylation and drop in cellular ATP content. The addition of fatty acids to the hepat ocyte incubation medium prevents the decrease in the metabolic rate. In spr ing, before spawning, a marked activation of energy metabolism in lamprey h epatocytes is found. These observations support the conclusion that the reg ulation of lamprey hepatocyte energy metabolism is realized through the ava ilability of fatty acids for oxidation. (C) 2000 Elsevier Science Inc. All rights reserved.