BIOCHEMICAL MEDICINE AND METABOLIC BIOLOGY 39, 148-157 (1988) Effects of Cold Stress on Serum Lipids, Lipoproteins, and the Activity of Lecithin: Cholesterol Acyltransferase in Rabbits C. TSOPANAKIS,* D. KOTSARELLIS,* I. DONTAS,* P. KARAYANNACOS,* AND G. SKALKEAS* Department of Experimental Physiology and *Laboratory for Experimental Surgery and Surgical Research, Athens University Medical School, Athens, Greece Received February 25, 1987, and in revised form July 15, 1987 Different kinds of stress to which an organism is subjected cause marked physiological changes, some of which could be of pathogenic importance. Changes in the physiological state of man influence not only the level of blood cholesterol but also the incidence of clinically manifested coronary heart disease (CHD) (1,2). The increased release of adrenocortical hormones accompanying stress has been reported to have profound effects on lipid and lipoprotein metabolism (3,4). Changes in lipid and lipoprotein levels are closely connected with atherosclerosis and CHD. Even slightly raised serum levels of cholesterol and triglycerides (5) are considered to be risk factors for the development of CHD and atherosclerosis in general (6). Studies concerning the distribution of cholesterol between different lipoprotein fractions have shown that although elevated low and very low density lipoprotein (LDL, VLDL) cholesterol were associated with increased risk, high density lipoprotein (HDL) cholesterol had a negative correlation with CHD (7). Any attempt to elucidate the physiological, pathobiochemical, or clinical significance of the different lipoproteins demands consideration of the multifactorial control mechanisms and factors regulating the lipoprotein system, among which are the enzymes involved in their metabolism (lipases and LCAT). It has been reported that rats fed with an atherogenic diet and exposed to stress exhibited a greater degree of hypercholesterolemia and coronary ather- osclerosis than their controls fed on the same diet (8), while exposure to cold and the ensuing stress have been found to have the same effects as other acute stress-producing conditions (9,lO). This study was initiated in order to investigate whether prolonged stress could mediate its effects on lipid metabolism, evoking changes in lipid and lipoprotein parameters comparable to those observed to accompany cardiovascular disease and atherosclerosis, and to contribute to the understanding of the possible links between stress-induced physiological changes and atherosclerosis and CHD. We report the results of subjecting normal and atherosclerotic rabbits to prolonged 148 0885-4505188 $3.00 Copyright 8 1988 by Academic Press, Inc. All rights of reproduction in any form reserved.