Protection of ischemic myocardium: the roles of nutrition and myocardial glycogen.
The ischemic myocardium utilizes glycogen as metabolic substrate. The effects of oral nutrition on the levels of glycogen in the myocardium and of myocardial glycogen content on myocardial tolerance to ischemia were studied. Rats were divided into groups and fed (a) rat chow, (b) rat chow plus 5% dextrose, and elemental diets (c) Flexical (Mead Johnson) or (d) Vital (Ross Laboratories). Another group was starved. All fed groups gained weight normally while the starved rats lost 23% of their body weight. Compared with the effect on rat chow, myocardial glycogen levels were elevated in the Flexical and starvation groups, while Vital depressed the level (P less than 0.01). Thus, both caloric intake and diet affected myocardial glycogen content. Elevation of myocardial glycogen content after starvation contrasted with glycogen disappearance from the liver. The level of myocardial glycogen and left ventricular function after global ischemia were correlated in dogs under cardiopulmonary bypass conditions. During 30 minutes of normothermic aortic cross-clamping, hearts with a preischemic myocardial glycogen content greater than 0.4 g% had less asystole or ventricular fibrillation. Their left ventricular function (stroke work index, myocardial contractility) upon reperfusion was substantially better than those with a myocardial glycogen level of less than 0.4 g%. Dietary manipulation and the nutritional status can thus affect the myocardial glycogen content and may be useful in protecting the myocardium from ischemia.
D000818:Animals; D003327:Coronary Disease / Q000378:metabolism*; D002149:Energy Intake; D005526:Food, Formulated; D006003:Glycogen / Q000032:analysis / Q000378:metabolism*; D006352:Heart Ventricles / Q000503:physiopathology; D008112:Liver Glycogen / Q000032:analysis; D008297:Male; D009200:Myocardial Contraction; D009206:Myocardium / Q000032:analysis*; D009751:Nutritional Requirements; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation; D013318:Stroke Volume
D008112:Liver Glycogen; D006003:Glycogen