Seasonal variations in the susceptibility of the aortic wall to atherosclerosis. Biochemical studies of glycosaminoglycans and collagen of rabbit atherosclerosis.

The aortic content of glycosaminoglycans and collagen as well as the uptake of [125 I] albumin were studied in 53 male albino rabbits during hair-shedding and outside the period of hair-shedding to elucidate the previously reported resistance to experimental arteriosclerosis during the shedding period [1]. The concentration of hyaluronic acid was highest during hair shedding, decreasing towards the non-shedding period. The content of dermatan sulphate, chondroitin-4, 6-sulphate and hydroxyproline was lowest during sheeding and highest outside the sheeding period. Accordingly, the incorportation of [35 S] sulphate in chondroitin -4, 6-sulphate and the dermatan plus heparan sulphate fraction was increased outside shedding, consistent with a stimulated synthesis. The concentration of hyaluronic acid was negatively correlated to the uptake of [125I] albumin, and the dermatan sulphate content was positively correlated to the content of hydroxyproline. The higher concentration of hyaluronic acid during the period of shedding may improve the elastic properties as well as the ability of the aortic wall to absorbe the haemodynamic strain involved in the vascular injury of this type of experimental arteriosclerosis [2]. The decrease in the concentration of hyaluronic acid simultaneously with an increase in the aortic content of collagen as well as of chondroitin-4, 6-sulphate and dermatan sulphate may imply a greater stiffness of the aorta resulting in a higher susceptibility to injury. The relationship between hyaluronic acid and [125 I] albumin is consistent with an importance of hyaluronic acid to the susceptibility of the arterial wall to deposition of macromolecules such as the lipids. Our observations represent an example of endogenous conditioned variations in the aortic content of glycosaminoglycans and hydroxyproline accompanied by a variation in the susceptibility to experimental arteriosclerosis.