EFFECTS OF HYPOXIA ON ENERGY-METABOLISM IN GOLDFISH HEPATOCYTES

The present study addresses the question whether long-term acclimation to hypoxia of the whole animal is accompanied by a chronic re-organiz ation of cellular function and metabolism To this end, long- and short -term effects of hypoxia on energy metabolism were studied in hepatocy tes isolated from goldfish acclimated to normoxia or hypoxia (10% air saturation). Aerobic (oxygen consumption) and anaerobic (lactate produ ction under chemical anoxia) ATP turnover was not affected by acclimat ion to hypoxia. The initial ATP content, a crude measure of energy sta tus, was elevated in hypoxia-acclimated cells compared with normoxic c ontrols but returned to control levels within 3 hr of normoxic exposur e. Na+ pump activity and the rate of protein synthesis were estimated from inhibitor sensitive rates of oxygen consumption. Neither of these two major ATP consumers of the cell was significantly altered by hypo xia acclimation, although Na+ pump activity showed a tendency to be el evated in the acclimated cells. During exposure to chemical anoxia, a pronounced decrease of lactate production was observed in hepatocytes that may have been related to metabolic acidosis. The decrease of anae robic energy output was not accompanied by a decrease of cellular [ATP ] and is therefore believed to reflect metabolic depression. The anaer obic energy metabolism of goldfish hepatocytes relies on ample glycoge n reserves and does not involve ethanol formation as a way to minimize acidotic load. (C) 1997 Elsevier Science Inc.