Chronic Alcohol Ingestion Alters the Calcium Permeability of Sarcoplasmic Reticulum of Rat Skeletal Muscle

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Abstract
Heavy sarcoplasmic reticulum (SR) was prepared from skeletal muscle of control and chroni alcoholic rats, and the effect of in vitro addition of ethanol on the passive Ca2+ permeability was studied. The SR was loaded with Ca2+ in the absence of ATP. Then efflux was initiated by adding an EGTA solution to decrease the extravesicular Ca2+ concentration. The decrease of Ca2+ content of the SR was measured by an optical method using an encapsulated metallochromic indicator (calcein). The Ca2+ permeability of alcoholic rat SR was higher than that of control rats, especially at low external Ca2+ concentrations (below 1 μM). An in vitro (acute) exposure of SR to ethanol increased the Ca2+ permeability of the SR. However, the degree of increase in alcoholic rat SR was smaller than that in control rat SR.