Effect of Acute and Chronic Alcohol Treatment and Their Superimposition on Lysosomal, Cytoplasmic, and Proteosomal Protease Activities in Rat Skeletal Muscle In Vivo

Alcohol can be considered as a nutritional toxin when ingested in excess amounts and leads to skeletal muscle myopathy. We hypothesized that altered protease activities contribute to this phenomenon, and that differential effects on protease activities may occur when: (1) rats at different stages in their development are administered alcohol in vivo; (2) acute ethanol treatment is superimposed on chronic alcohol-feeding in vivo; and (3) muscles are exposed to alcohol and acetaldehyde in vivo and in vitro. In acute studies, rats weighing approximately 0.1 kg (designated immature) or approximately 0.25 kg (designated mature) body weight (BW) were dosed acutely with alcohol (75 mmol/kg BW; intraperitoneal [IP], 2.5 hours prior to killing) or identically treated with 0.15 mol/L NaCl as controls. In chronic studies, rats (approximately 0.1 kg BW) were fed between 1 to 6 weeks, with 35 % of dietary energy as ethanol, controls were identically treated with isocaloric glucose. Other studies included administration of cyanamide (aldehyde dehydrogenase inhibitor) in vivo or addition of alcohol and acetal-dehyde to muscle preparations in vitro. At the end of the treatments, cytoplasmic (alanyl-, arginyl-, leucyl-, prolyl-, tripeptidyl