Hypotensive effects of captopril on physical properties of the arterial system in young and adult rats

We determined the acute effects of the angiotension converting enzyme inhib itor captopril on the arterial mechanics in rats at different ages, based o n the exponentially tapered T-tube model. Male Wistar-Kyoto rats aged 4 and 12 months were individually referred to as young (n = 8) and adult rats (n = 8) and were anesthetized and thoractomized. The pulsatile aortic pressur e and flow signals before and after the administration of captopril 120 mg/ kg, i,p.) were measured by a high-fidelity pressure sensor and an electroma gnetic flow probe, respectively. In each age group, captopril showed little change in basal heart I ate as well as cardiac output. However, captopril produced a drop of 15% in mean aortic pressure in young and a fall of 12% i n adult rats. In addition, captopril reduced total peripheral resistance by 21% in young and by 23% in adult animals. As for the pulsatile nature of t he arterial system, captopril had increased wave transit time of the lower body circulation of 10% in young and of 12% in adult rats. By contrast, cap topril reduced wave reflection factor by 22% in young and by 25% in adult a nimals. in conclusion, the converting enzyme inhibitor captopril has a stif fness-decreasing effect on Windkessel vessels and a dilated effect on resis tance arterioles in either young or adult rats. No age dependence of vascul ar response and reflex tachycardia to captopril has been found in rats betw een 4 and 12 months.