GLUCOCORTICOID EFFECTS ON VASCULAR CONNECTIVE TISSUE DURING REPAIR. IMPORTANCE OF DOSE LEVEL AND PRE- AND POST-INJURY TREATMENT

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Abstract
Aorta of male albino rabbits were subjected to a single mechanical dilatation injury and effects of different daily doses of prednisolone on the metabolism of collagen and glycosaminoglycans and on the content of .alpha.-amino nitrogen, RNA, DNA, water and fat and the histology of the descending thoracic aorta were analyzed 10 days after the injury. Effects of pre- and post-injury treatment with prednisolone were compared. Prednisolone inhibited the intimal thickening. This effect was enhanced by pre-injury treatment. Prednisolone inhibited biosynthesis of non-dialyzable 14C-hydroxyproline-collagen but increased the relative degradation of collagen in a dose dependent manner. The biosynthesis of glycosaminoglycans was decreased, while prednisolone had no effect on concentration and total amount of glycosaminoglcyans, collagen, protein, RNA, DNA and fat. The aortic content of water was decreased during treatment with prednisolone also in a dose dependent manner. The action of prednisolone on vascular collagen and water during repair apparently is dose dependent, and the inhibitory action of prednisolone on the intimal thickening apparently is enhanced by pre-injury treatment.