The effect of a fat-rich diet on the ultrastructure of mesenteric arteries of the rat and their reaction to local desendothelialization.

By comparison with the previously described results of similar experiments performed on normal rats (Potvliege and Bourgain, 1976, 1980), it was observed that with a fat-rich diet the endothelium contained a greater number of Weibel-Palade bodies and that there was an increased tendency for blood monocytes to stick to the endothelium as well as for platelets to form, small, non-adherent aggregates particularly at sites of arterial branching opposite intimal cushions. The intimal cushions were larger and they reacted to local thrombogenic treatment by greater and more prolonged myointimal growth. In addition, although their endothelial lining did not become detached, individual cells showed signs of degeneration. These changes are interpreted as indicating that a fat-rich diet enhances atherogenesis at points of greater haemodynamic stress by locally increasing intraluminal platelet aggregation and endothelial-cell degeneration. These 2 ever-recurring events favour, in the former case, a slow but steady liberation of platelet factors, and, in the latter, an easier penetration into the artery wall of mitogenic substances which stimulate myointimal growth. The adhesion of monocytes to the endothelium may represent a first step towards their migration into the intima where, at a later stage, they may become transformed into foam cells, thus completing the atherogenic cycle.