Breed differences in the responses of rabbits to atherogenic diets

New Zealand White and Dutch rabbits differ markedly in their susceptibility to induction of both hypercholesteremia and atheroma by diets ranging in cholesterol content from 0.1 to 1.0 %. In rabbits fed 0.25 % cholesterol for 3 months liver biopsies were taken at monthly intervals and used to measure in vitro incorporation of [ 14C]-acetate into cholesterol. Although serum cholesterol rose slightly in the Dutch and markedly in the New Zealand Whites this level of dietary cholesterol did not influence precursor incorporation into liver cholesterol of either breed, indicating the absence of feedback sensitivity to the levels attained by this feeding regime. Liver cholesterol content increased some 5-fold in both breeds and sexes indicating that initial absorption of the sterol was not different. However, serum cholesterol remained low in the Dutch, especially in the males, suggesting their ability to prevent cholesterol efflux from the liver into the systemic circulation. The decay of endogenously labeled [ 14C]-cholesterol in plasma tested at the end of 5 months revealed no greater ability of the resistant Dutch rabbits to catabolize and/or excrete cholesterol. In fact, paradoxically, cholesterol-fed males demonstrated greatly increased turnover time in both strains, although due to the small number of animals no precise calculation of this parameter was attempted.