Effect of an hypercholesterolemic diet on the level of several serum lipids and apolipoproteins in nine rat strains.

To detect the response of different strains of rats to an hypercholesterolemic diet, 9 different strains of male rats were fed successively a control diet (C) containing 20% casein for 4 weeks, then a high-protein, cholesterol-rich diet (HC) containing 50% casein and 1.2% cholesterol for 12 weeks. When the rats were fed the control diet, the highest cholesterolemia was found in the LOU strain and the lowest in the WAG and Brown-Norway (BN) strains. The latter strain had the highest free to esterified cholesterol ratio and showed a marked band in beta position (LDL) on agarose gel electrophoresis. Administration of the HC diet induced an increase of cholesterolemia in all the strains except in Fisher (FIS) and LOU. This hypercholesterolemic diet decreased the free to esterified cholesterol ratio only in the BN and FIS strains. On agarose gel, all the strains showed a highly increased band in pre-beta position (VLDL). On polyacrylamide gel, a single, tight band in HDL position was revealed in the BN strain, while a large band or two bands were seen in the other strains. The percentages of some apoproteins in serum total lipoproteins were determined in rats fed the HC diet; the apoprotein E level was inversely correlated to the difference between the cholesterolemia of the rats given the HC and C diets (r = - 0.72; P less than 0.05). So, the BN rats had the lowest apo E level with the highest cholesterolemia increase due to the HC diet.