Further Studies on the Reversibility of Serum Sickness Cholesterol-induced Atherosclerosis

Rabbits were induced to form atheromatous cardiovascular lesions by subjecting them to treatments of a single BSA injection plus a 2-wk period of cholesterol diet, or to the diet alone. Microscopic examination of the hearts at the end of the 2-wk induction period, or after having been returned to regular diet for 5 or 8 wk, showed that lesion incidence in the cholesterol-only animall decreased markedly during the 8-wk rest period, while little change in incidence occurred in animals with lesions from the combined treatment. This finding was taken to mean that the latter type of lesion was less reversible, and therefore perhaps more pathologically significant, than the former type. It was felt that lipid deposition was not solely responsible for this prolongation, since it was present in diet-only lesions which disappeared with time, and also seemed to be disappearing from the prolonged lesions in all treatment groups. On the other hand, elastic tissue was demonstrated only in lesions arising from the combined treatment, and it is hypothesized that this feature is implicated in the prolongation of these lesions.