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 inhibitor captopril on the arterial mechanics in rats at different ages, based on 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 wereanesthetized and thoractomized. The pulsatile aortic pressure andflow signals before and after the administration of captopril (20mg/kg, i.p.) were measured by a high-fidelity pressure sensor andan electromagnetic flow probe, respectively. In each age group,captopril showed little change in basal heart rate as well ascardiac output. However, captopril produced a drop of 15% in meanaortic pressure in young and a fall of 12% in adult rats. Inaddition, captopril reduced total peripheral resistance by 21% inyoung and by 23% in adult animals. As for the pulsatile nature ofthe arterial system, captopril had increased wave transit time ofthe lower body circulation of 10% in young and of 12% in adultrats. By contrast, captopril reduced wave reflection factor by22% in young and by 25% in adult animals. In conclusion, theconverting enzyme inhibitor captopril has a stiffness-decreasingeffect on Windkessel vessels and a dilated effect on resistancearterioles in either young or adult rats. No age dependence ofvascular response and reflex tachycardia to captopril has beenfound in rats between 4 and 12 months.