CHOLESTEROL INDUCED LIPID-ACCUMULATION IN MYOCARDIAL-CELLS IN RATS

Objective: The aim was to investigate whether cholesterol feeding of rats for only 10 d would result in lipid accumulation in myocardial cells and a change in the peroxisomal beta oxidation in the heart compared to the hearts of rats on standard feeds. Methods: Eight rats received a cholesterol diet (2%) and eight rats received a standard diet for 10 d. Lipids were measured in serum, liver, and heart. Palmitoyl-CoA hydrolase and fatty acyl-CoA oxidase were determined in total homogenate of hearts. The fractional volume of lipid droplets in myocardial cells was calculated from micrographs at a magnification of X9600 obtained by electron microscopy. Results: The fractional volume of lipid droplets in the cardiomyocytes increased from 0.109(SEM 0.019)% to 0.259(0.037)%, (p<0.003), as a result of cholesterol feeding. Cholesterol and triglycerides in the heart measured by biochemical methods increased by 13% and 24%, respectively. There was no difference in palmitoyl-CoA hydrolase or fatty acyl-CoA oxidase in the hearts of the cholesterol fed group compared to the control group, suggesting an unaltered peroxisomal beta oxidation of fatty acids in the myocardium. The serum triglycerides and serum phospholipids were reduced in the cholesterol fed rats (p<0.05 and p<0.001, respectively). Rats fed cholesterol diet showed a reduced ratio of HDL cholesterol to total cholesterol in serum, together with an increased liver weight and relative liver weight compared to the control rats. The addition of cholesterol to the diet increased liver cholesterol to 21.0(1.6) mumol-g-1 wet weight compared to 5.87(0.93) mumol.g-1 in the controls on standard diet (p<0.0001). Cholesterol feeding had no effect on the hepatic level of phospholipids, but the liver triglycerides tended to increase from 23.3(9.5) mumol.g-1 wet weight to 53.3(6.3) mumol.g-1. Conclusions: Lipid accumulation in the myocardial cells was shown by morphometry after 10 d of cholesterol feeding, without any visible damage to the tissue.