Angiotensin type 2 receptor in resistance arteries of type 2 diabetic hypertensive patients

The role of angiotensin type 2 receptor (AT(2)R) on vascular responses to angiotensin II in humans remains unclear. In this study we explored whether AT2R is expressed and functionally active on peripheral resistance arteries of hypertensive diabetic patients treated for 1 year with either the angiotensin receptor blocker valsartan or the beta-blocker atenolol. Twenty-six hypertensive type 2 diabetic patients treated with oral hypoglycemic and antihypertensive agents (not receiving angiotensin receptor blockers or beta-blockers) were randomly assigned to double-blind treatment for 1 year with valsartan or atenolol once daily added to their previous therapy in a clinical trial that we reported recently and compared with 10 normal subjects. Resistance arteries dissected from gluteal subcutaneous tissues were assessed on a pressurized myograph. Vasomotor response curves to angiotensin II (1 nmol/L to 1 mu mol/L) were performed on norepinephrine precontracted vessels in the presence of valsartan (10 mu mol/L) with or without the AT(2)R inhibitor PD123319 (1 mu mol/ L). AT(2)R expression was evaluated by confocal microscopy. After 1 year of treatment, systolic and diastolic blood pressure was controlled and comparable in the valsartan and atenolol groups. Angiotensin II evoked a significant vasodilatory response only on resistance arteries from patients treated with valsartan, effect blocked by PD123319. AT(2)R expression was 4-fold higher in small arteries of valsartan-treated patients. In conclusion, AT(2)Rs are upregulated and contribute to angiotensin II-induced vasodilation in resistance arteries of hypertensive diabetic patients treated with angiotensin type 1 receptor blockers and may mediate, in part, vascular actions of these drugs in high cardiovascular risk patients.