Vasorelaxant effect and mechanisms of compound reserpine and triamterene tablets on the isolated thoracic aorta rings

This study aimed to evaluate the vasorelaxant effect and mechanisms of compound reserpine and triamterene tablets (CRTTs) and its component triamterene on isolated rat thoracic aorta rings. Isolated rat thoracic aorta rings pre-contracted by high potassium or norepinephrine (NE) were used to evaluate the vasodilatory effect of CRTTs and its component triamterene. The mechanisms concerning endothelium, potassium channels and calcium channels were studied through the interventions of several tool drugs. Animal welfare and experimental procedures followed the requirements of the Laboratory Animal Management and Animal Welfare Ethics Committee of the Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College. The results showed that both CRTTs and triamterene had potent relaxant effect on KCl and NE pre-contracted vessels. Triamterene showed partial endothelium dependency, and N-nitro-L-argininemethyl ester hydrochloride (L-NAME) could influence the relaxant effect, which may be related to the opening of calcium-activated potassium channels. Meanwhile, CRTTs could inhibit intracellular Ca²⁺ release and extracellular Ca²⁺ influx. Overall, CRTTs and its component triamterene have vasorelaxant effects on vessels in vitro, and the vasorelaxant effect of CRTTs may be related to intracellular Ca²⁺ release and extracellular Ca²⁺ influx, while this effect of triamterene may depend on vascular endothelial function and may also be related to the opening of calcium-activated potassium channels.