The hypothesis proposed in these investigations is that ethanol consumption impairs the transport of precursor proteins into the mitochondrion, and therefore affects mitochondrial function and assembly. The experiments proposed will seek to determine 1) if ethanol and acetaldehyde can directly affect the ability of hepatic mitochondria to import and process a specific precursor protein and 2) if chronic ethanol administration affects the import and processing activity of isolated liver mitochondria. The methodology proposed is the use of an in vitro translation/mitochondrial import assay in which radioactive proteins will first be synthesized in vitro using lysates of rabbit reticulocytes programmed with rat liver RNA. The radiolabelled translation products will then be incubated with isolated rat liver mitochondria and, the import and processing of proteins in general and, in particular, of the mitochondrial enzyme glutamate dehydrogenase (GDH), will be measured. The latter assay will determine the amount of higher molecular weight precursor GDH that is converted to the mature, lower molecular weight form of the enzyme. These experiments specifically seek to determine whether mitochondrial import is impaired by ethanol consumption and whether this may contribute to the ethanol-induced abnormalities in mitochondrial structure and function reported by others. Alcohol-induced impairment of normal mitochondrial function may contribute to the pathogenesis of alcoholic liver disease since many other energy-requiring cellular activities are dependent on normal mitochondrial energy generation. If mitochondrial import is shown to be altered by ethanol and/or acetaldehyde in the proposed experiments, it will be one of the first direct demonstrations of a mechanism which may explain how ethanol consumption can significantly alter the structure and function of this organelle.
