RESUMEN
OBJECTIVE: The aim was to investigate the effect of diets with different lipid content on rat myocardial tissue lipid composition and their possible influence on myocardial electrical activity. METHODS: 60 male Sprague-Dawley rats were randomised in three dietary feeding groups. Half the animals were used for the myocardial lipid study and the other half for the ventricular refractory period and ventricular conduction velocity measurements. Synthetic diets of low fat, high fat (predominantly lard fat), and high fat plus marine oil, the last two with cholesterol, were supplied ad libitum for five weeks. After 2-propanol myocardial lipid extraction, lipid fractions were separated by thin layer chromatography and their esterified fatty acids by gas-liquid chromatography. Ventricular refractory period was obtained according to the extrastimulus technique and maximum conduction velocity by ventricular pacing. RESULTS: The experimental diets induced marked changes in fatty acid composition of myocardial phospholipids and in esterified cholesterol content. The high fat group showed a significant decrement in oleic and linoleic acids, with an increment in arachidonic and docosahexaenoic acids in their phospholipid composition. This dietary group had the highest esterified cholesterol content. These changes were related to lowering of maximum ventricular paced heart rate and lengthening of ventricular refractory period, and were partly corrected by marine oil supplement. CONCLUSIONS: Saturated fat diets cause profound changes in myocardial fatty acyl composition which are linked to sustained differences in myocardial electrical activity. These changes can be partly corrected by a moderate fish oil supplement.