Effects of chronic graded ethanol consumption on the metabolism, ultrastructure, and mechanical function of the rat heart.

Three sequential sets of ethanolic rats (E) and their matched controls (C) were fed regular chow containing standard vitamins with the ethanol group in each series also receiving a progressively greater alcohol intake for 3 to 6 months: E1 5%, E2 10%, and E3 25% ethanol. Electron microscopy showed swelling of mitochondria, transverse tubules and sarcoplasmic reticulum, dehiscence of intercalated discs and disintegration of myofibrils scattered throughout the ventricular myocardium in E1 and E2 as early as 7 wk after beginning 5% ethanol; in addition, there were clumping of mitochondria and supercontraction of myofibrils in E3. Concomitant with substructural abnormalities in E3, there were slight but significant depressions of cardiac myofibrillar ATPase activity and mitochondrial function. Cardiac catecholamines, hydroxyproline, and total bound glycerol were unchanged. Alteration of isometric contraction of isolated, supported left ventricular papillary muscles occurred initially in E2 and was clearly evident in E3 by significant reduction of duration of systolic active state (time from onset to peak tension), while total tension generated and peak rate of tension rise were not yet disturbed. Extra vitamin supplementation in additional rats drinking 25% ethanol minimally lessened decline in myofibrillar ATPase activity, but otherwise provided no protection. Thus, chronic daily ingestion of graded quantities of ethanol representing 10 to 30% of total calories in well-nourished animals exerted toxic effects on microstructure, metabolism and mechanics of the ventricle. These alterations are postulated to be pertinent to early pathogenesis of clinical alcoholic cardiomyopathy.