COMPARISON OF THE INFLUENCE OF DIETARY SATURATED FAT AND AGING IN THELIPID-COMPOSITION AND BIOELECTRICAL ACTIVITY OF RAT MYOCARDIUM

Background: Age and diet have been related to the lipid composition an d function of biologic tissues. Methods: We studied three groups of 20 Sprague-Dawley rats divided on the basis of age and diet: low-fat die t in rats 3 months of age, high saturated fat diet in rats 3 months of age, and low-fat diet in 20-month-old rats. Myocardial lipid composit ion (content of phosphatidylcholine, phosphatidylethanolamine, triglyc erides, cardiolipin, and cholesterol, and their fatty acid composition ) was analyzed by quantitative thin-layer and gas liquid chromatograph y. Ventricular refractory period was obtained. Results: Lipid analysis showed significant changes (P<0.05) in rats on a high-fat diet and in the aged group versus the young group on a low-fat diet: increment in stearic (C18:0) and arachidonic acids (C20:4) acids and decrement in linoleic acid (C18:2) in phosphatidylcholine; increment in docosahexae onic acid (C22.6) and decrement in C18:2 in phosphatidylethanolamine; increment in oleic acid (C18:1) in cardiolipin; increment in C18:1 and decrement in C18:2 in triglycerides. Mean ventricular refractory peri od was 90 +/- 10 ms in young animals on a low-fat diet, 121 +/- 8 ms i n young animals on a high-fat diet, and 113+/-4 ms in old animals on a low-fat diet (P < 0.05). Conclusions: Thus, cholesterol levels, fatty acid composition, and electrical activity of rat myocardial tissue ar e similar in old rats fed a low-fat diet and in young rats fed a diet high in saturated fat.