DIETARY FISH OIL ADDED TO A HYPERLIPIDEMIC DIET FOR SWINE RESULTS IN REDUCTION IN THE EXCESSIVE NUMBER OF MONOCYTES ATTACHED TO ARTERIAL ENDOTHELIUM

Modest numbers of blood monocytes become attached at least temporarily to the endothelium of large arteries in normal swine fed low fat, low cholesterol diets. These numbers are increased several fold when the swine are fed a high saturated fat, high cholesterol atherogenic diet (BT). The main objective of this portion of a broader study was to see if the addition of fish oil (30 ml) to a BT diet (BT + FO) could prevent the increase in attached monocytes induced over arterial endothelium in BT fed swine. Six BT, 6 BT + FO and 5 control mash (MA) swine fed the respective diets for 4 months before killing were available for the current study. Other aspects of this experiment have been presented previously which in brief are that BT + FO resulted in retardation of atherosclerotic lesion development and a shift in lipoprotein components from predominantly apolipoprotein B,E containing with the BT diet to predominantly apo B only with BT + FO. There was a significant positive correlation between lesion development and apo B,E lipoproteins. In the current study we determined by scanning electron microscopy on the first portion of the left anterior descending coronary artery after perfusion fixation under pressure the number of monocytes per mm2 attached over or not over visible lesions. We also determined monocyte percentages in the circulating blood and analyzed the correlation of the numbers of attached monocytes and blood monocyte percentages with various lipoprotein components reported previously. The values for attached monocytes over lesions were for BT 570 ± 111, BT + FO 264 ± 56, MA 69 ± 8 per mm2 and all differences are significant. Corresponding values for monocytes not over lesions were: BT 85 ± 8, BT + FO 115 ± 48, MA 143 ± 31 per mm2. None of the differences is signficant. The attachment of the monocytes appeared generally to be by protrusion of pseudopodes between endothelial cells which otherwise appeared undamaged. The percentages of monocytes in the circulating blood were: BT 19 ± 2, BT + FO 11 ± 1, MA 11 ± 1 with BT significantly greater than the other two. Studies of correlations with plasma lipoprotein components showed significant correlations of both attached monocytes over lesions and percentage blood monocytes with apo B,E lipoproteins but a negative or no significant correlation with apo B only lipoproteins (conventional LDL). © 1990.