THE INFLUENCE OF HYPOXIA AND ANOXIA ON DISTRIBUTION OF ADENINE-NUCLEOTIDES IN ISOLATED HEPATOCYTES

Isolated hepatocytes incubated under conditions of ''chemical hypoxia' ' (KCN + iodoacetic acid) exhibited a marked dephosphorylation of the cytoplasmic and mitochondrial adenine nucleotides to AMP. Cytoplasmic adenine nucleotide levels (ATP + ADP + AMP) were decreased by 40%. The re was no significant change in the mitochondrial adenine nucleotide p ool size. For starved rats, but not for fed rats, addition of KCN to i solated hepatocytes resulted in a shift of the mitochondrial adenine n ucleotide species to AMP. This difference was correlated with the main tenance of a substantial level of cytoplasmic ATP in the fed vs starve d condition, The addition of fructose (but not glucose) to hepatocytes isolated from a starved rat, prevented the KCN-induced dephosphorylat ion of mitochondrial adenine nucleotides to AMP. Fructose-treated cell s had a significant level of ATP in the cytoplasm, whereas glucose-tre ated cells did not. Addition of A23187 to fructose-treated (but not gl ucose-treated) cells resulted in a net loss in the mitochondrial adeni ne nucleotide content. The results suggest that the shift of matrix ad enine nucleotides from ATP and ADP to AMP preserves the mitochondrial adenine nucleotide pool size during transient hypoxia by preventing ne t adenine nucleotide transport to the cytoplasm via the ATP-Mg/P-i car rier. This effectively protects those adenine nucleotides from the cyt oplasmic purine degradation pathway, a strategy that has the potential to facilitate rapid recovery of bioenergetic status by oxidative phos phorylation upon reoxygenation. (C) 1994 Academic Press,Inc.