Elastase, collagenase, and cathepsin D activities in the aortas of spontaneously hypertensive and renal hypertensive rats

In an attempt to clarify the roles of proteases in the developmental mechanisms of hypertensive vascular lesions, changes in activities of aortic elastase, collagenase, and cathepsin D in spontaneously hypertensive rats (SHR) and renal hypertensive rats were biochemically investigated. In SHR, elastase activity initially showed a significant increase, once two-fold higher than that in the control; but the activity tended to decrease earlier than that in the control. In both SHR and normotensive control rats collagenase activities tended to increase with advancing age. The activity in SHR was two-fold higher than that in the control at all ages examined. In both younger SHR and normotensive rats cathepsin D activities proved to be increased with advancing age, while in old rats the activities tended to decrease. The activity in SHR was three- to fivefold higher than that in the control at all ages examined. In renal hypertensive rats, the activities of elastase, collagenase, and cathepsin D increased gradually with increasing blood pressure, at levels significantly higher than those in the control. These findings suggest that the metabolisms of proteins such as elastin and collagen, expressed by these enzyme activities, are accelerated under hypertensive conditions.