Effects of long-term blockade of angiotensin converting enzyme with captopril on blood pressure and aortic prolyl hydroxylase activity in spontaneously hypertensive rats.

In order to determine if long-term treatment with captopril affects vascular collagen biosynthesis we administered the agent at a dose of 30 or 100 mg/kg/day p.o. for 6 weeks to spontaneously hypertensive rats. At the 6th week of captopril treatment the aorta was excised and the activity of prolyl hydroxylase, the rate-limiting enzyme of collagen biosynthesis, was measured. Vascular enzyme activity was decreased by 7.0% and 34.6% in the low- and high-dose groups, respectively. A single oral administration of captopril, on the other hand, did not decrease the enzyme activity in the aorta. Furthermore, captopril had no direct inhibitory effect on the enzyme activity in vitro. These findings suggest that the decrease in vascular prolyl hydroxylase activity resulted from a sustained decrease in blood pressure.