Quinapril effects on resistance artery structure and function in hypertension

The effects of chronic treatment with quinapril on blood pressure, vascular reactivity and structure of resistance arteries were examined in adult, male spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. SHR and WKY at 15 weeks of age were treated with quinapril (10 mg/kg per day) for 10 weeks. Structural changes in the mesenteric arteries were measured by optical sectioning with confocal microscopy and in renal arteries by light microscopic measurements. Apoptotic cells in the mesenteric vessel wall were identified using the terminal deoxynucleotide transferase-mediated dUTP-nick end-labelling (TUNEL) method. The response of mesenteric arteries to noradrenaline, electrical stimulation, acetylcholine and sodium nitroprusside was studied using a pressure myograph system. Treatment with quinapril significantly lowered systolic blood pressure and ventricular weight in both SHR and WKY. It reduced wall thickness and medial volume in mesenteric arteries from SHR and WKY and media-to-lumen ratio in interlobular arteries of SHR. It also decreased the number of smooth muscle layers in SHR and increased the number of apoptotic smooth muscle cells in both SHR and WKY. In addition, treatment normalized the augmented contractile responses and improved the impaired relaxation response of SHR mesenteric arteries to the level of WKY. We conclude that treatment with quinapril lowered blood pressure and improved cardiac and vessel structure and vessel function. An increase in apoptotic process of medial smooth muscle cells is one of the mechanisms underlying the vascular structural improvement.