Effects of Isoflurane Dose, Duration of Anoxia, and Reoxygenation on Isoflurane??s Preservation of Energy Balance in Anoxic Isolated Hepatocytes

Abstract

We investigated how the protection of energy status by isoflurane in isolated hepatocytes varied with isoflurane dose, duration of anoxia, and reoxygenation. Hepatocytes were isolated from fed rats and incubated in Krebs buffer under O2/CO2 or N2/CO2 (95/5) for 30 or 90 min, followed by 5 or 30 min of reoxygenation. From measurements of adenosine tri-, di-, and monophosphate (ATP, ADP, AMP) in the cells, energy charge (= [ATP + 1/2 ADP]/[ATP + ADP + AMP]) was calculated to reflect the balance between ATP supply and demand, and total adenine nucleotide (= ATP + ADP + AMP) to indicate the potential maximum ATP level. During 30 min of anoxia, energy charge and total adenine nucleotide steadily increased with isoflurane dose from 0 to 2 minimum alveolar anesthetic concentration, then decreased from 2 to 3 minimum alveolar anesthetic concentration. In short incubations (30-35 min) at 1 minimum alveolar anesthetic concentration isoflurane, there was a modest decrease in energy charge during anoxia, partially prevented by isoflurane and completely reversed by reoxygenation, and no decrease in total adenine nucleotide. In long incubations (90-120 min), there were large decreases in both energy charge and total adenine nucleotide during anoxia, with partial and no reversal by reoxygenation, respectively. Isoflurane partly prevented decreases in both energy charge and total adenine nucleotide during both anoxia and reoxygenation. We conclude that at doses in the clinical range, isoflurane partially protected isolated hepatocytes against decreases in both energy charge and total adenine nucleotide occurring either during short (reversible) or long (irreversible) anoxia.(ABSTRACT TRUNCATED AT 250 WORDS)