Effects of halothane, enflurane and isoflurane on some energy-converting functions of isolated rat liver mitochondria.

Enflurane and isoflurane appeared equally effective in decreasing the efficiency of oxidative phosphorylation in isolated mitochondria, while halothane was twice as effective as these two anesthetics. On the other hand enflurane and isoflurane exhibited different dose-response relationships when the uptake of calcium was measured (with a calcium-selective electrode) or the transmembrane electrical potential was monitored (with tetraphenylphosphonium-selective electrode) during ATP synthesis or calcium uptake in anesthetic treated mitochondria. The results indicate that the effects of isoflurane and enflurane on the mitochondrial energy converting processes are qualitatively, but not quantitatively, analogous to those previously described for halothane. Moreover the damaging action of isoflurane gradually increases as the anesthetic concentration increases, while that of enflurane suddenly increases above a threshold concentration. It appears that the effects of halothane, enflurane and isoflurane on isolated mitochondria involve both the ATP synthetase and the inner membrane permeability barrier, although the membrane-anesthetic interactions responsible for such effects are probably different for each anesthetic.