Hepatic cell membrane potential (HCMP) and protein synthesis were studied in rats during and after a period (60 min) of liver ischemia. ATP-MgCl2 (5 mumol . 100 g bw-1) or saline was administered slowly intravenously before or after the period of liver ischemia. No beneficial effect of ATP-MgCl2 on the impaired HCMP or protein synthesis was observed. On the contrary, the post-ischemic restitution of these cellular metabolic variables was slower in animals receiving ATP-MgCl2 after the period of liver ischemia as compared with saline-treated rats. At the end of the ischemic period, ATP, glucose and lactate in liver tissue were the same in animals receiving ATP-MgCl2 or saline before ischemia. These results suggest that the beneficial effects previously reported after administration of ATP-MgCl2 in conditions with reduced hepatic blood flow are not primarily due to an improved metabolic situation in the liver.