Long-term effect of glucocorticoid on connective tissue of aorta and skin Morphological and biochemical studies of tissues from rabbits with intact and injured aortas

The long-term effect of prednisolone — 0.6 mg/day for 63 days — upon mechanically induced inflammation and repair processes in vascular connective tissue was compared with that upon undamaged vascular wall and intact skin of rabbits. The investigations included histological examination of aorta as well as biochemical analyses of collagen and various glycosaminoglycan fractions, RNA, DNA and alpha-amino nitrogen. The metabolism of collagen was estimated by in vitro labelling with [14C]proline and the metabolism of glycosaminoglycans by in vivo labelling with [35S]O4. The radioactivity of [125I]albumin in the aorta and serum was also studied. The collagen, glycosaminoglycans, RNA, DNA and water of vascular connective tissue during inflammation and repair and of intact skin was found to be more sensitive to the action of prednisolone than the connective tissue of undamaged vascular wall. An increased degradation of newly synthesized collagen was observed in damaged aorta as well as in skin in which also the biosynthesis of collagen was inhibited. Prednisolone inhibited the biosynthesis of glycosaminoglycans and decreased the total amount of glycosaminoglycans and of nucleic acids in the damaged aortas and the skin. The [125I]albumin aorta-to-serum ratio was significantly increased in the damaged aorta. Prednisolone treatment decreased the ratio in injured aortas, but elevated the ratio in the undamaged vessels. Prednisolone inhibited intimal thickening of the injured aortas.