Atherosclerosis; inhibiting effect of an antihistaminic drug, chlorpheniramine.

• Atherosclerotic lesions tend to form in areas of the vascular tree subjected to injury —usually mechanical injury. Since injury enhances the phagocytic activity of endothelial cells,' the possibility arises that localization of lipid material may be due in part to phagocytosis of serum lipoproteins by injury-activated aortic endothelial cells. Supporting this possibility is the observation that endothelial cells overlying foam cell plaques formed in cholesterol-fed rabbits display phagocytic activity toward intravenously injected colloidal thorium dioxide.' In addition, electron microscope studies of these endothelial cells are interpreted as indicating that they are actively removing lipoproteins from the blood by pinocytosis,' a process believed to be basically similar to that of phagocytosis.' Phagocytosis and/or pinocytosis are further implicated in atherosclerosis in that the foam cell plaques of cholesterolinduced rabbit atherosclerosis, similar in appearance to the fatty streaks or flecks generally considered to be the first gross manifestation of human atherosclerosis, seem to be produced by an aggregation of fat-filled cells (presumably smooth muscles and/or macrophages) that have taken up lipid material deposited in the subendothelial space.-