Isoflurane partially preserves energy balance in isolated hepatocytes during in vitro anoxia

We investigated whether a volatile anesthetic (1.5% isoflurane or 1.0% halothane) or an added anaerobic energy source (10 mM glucose or fructose) could act directly on liver cells to protect energy status during 20-30 min of anoxia. We used hepatocytes freshly isolated from fed rats or rats that had fasted, suspended them in Krebs' buffer, and incubated them in sealed flasks under O₂/CO₂ or N₂/CO₂ (95%:5%). The adenosine triphosphate (ATP) to adenosine diphosphate (ADP) ratio (ATP/ADP) measured cellular energy balance-the balance between overall ATP supply and demand. Lactate levels measured the extent to which ATP was supplied by the nonmitochondrial pathway, (anaerobic) glycolysis. Maximum values of energy balance were seen in cells from fed rats incubated in the presence of glucose and O₂. When glucose was replaced by fructose, ATP/ADP decreased and lactate increased. During anoxia (O₂ replaced by N₂), increases in lactate were also seen with glucose; and ATP/ADP decreased to similarly low values with both substrates. In cells from fasted rats, ATP/ADP decreased significantly below the value for cells from fed rats only in the presence of glucose and O₂. Compared with cells from fed rats, cells from fasted rats showed decreased lactate in the face of decreased ATP/ADP, suggesting that glycolysis was impaired. Isoflurane partially prevented anoxia-induced decreases in ATP/ADP. This protective effect on energy balance occurred equally with glucose and fructose, but was not seen in cells from fasted rats or with halothane. Thus, 1 MAC isoflurane and some factor(s) related to the fed state combined to protect partially the energy balance in anoxic liver cells through action(s) at the cellular level. The molecular mechanisms of these effects remain to be determined. Further studies will also be needed in more intact systems to determine whether these energy-protective effects of volatile anesthetic and nutritional status influence hepatic preservation under clinically relevant conditions of anoxia and ischemia.