Release of mitochondrial rather than cytosolic enzymes during liver regeneration in ethanol-intoxicated rats

Abstract

Background Partial hepatectomy (PH) promoted rapid increase in serum of hepatic enzyme activities localized in mitochondria preferentially to increase enzyme activities from cytosol; low doses of ethanol (EtOH) administered to PH rats expedited return to normality of these elevated serum enzyme activities. The fate of released mitochondrial enzymes from liver was investigated in this study to advance knowledge of the role of mitochondria during priming phase of liver regeneration. Methods Catalytic activity of mitochondrial and cytosolic proteins was measured in remnant liver after PH and in elutes of perfused remnant livers from control and ethanol-intoxicated rats. Results During the first 24 h of liver regeneration (LR), mitochondrial enzymes—glutamate dehydrogenase, aspartate amino transferase, and malate dehydrogenase—diminished 33–58% in mitochondria, increased 17% in cytosol, and for two enzymes rose 68–86% in perfusates. Cytosolic lactate dehydrogenase decreased transiently in cytosol (24%) and increased only 13% in perfusates. Activity of cyclooxygenase I (mitochondrial membrane-attached enzymes) was not modified. Ethanol intoxication after PH produced earlier and slightly higher extrusion of matrix mitochondrial enzyme activities. Conclusions Selective increase of mitochondrial membrane permeability appeared as an important event during priming phase of LR after PH, thus sustaining preferential release of mitochondrial proteins outside the organelle in comparison with limited redistribution of cytosolic and mitochondrial membrane proteins. High doses of EtOH delayed LR and re-enforced mobilization of proteins produced by PH probably by enhancing greater mitochondrial membrane permeability.