Angiotensin II type 1 receptor is involved in flow-induced vasomotor responses of isolated middle cerebral arteries. Role of oxidative stress

This study aimed to determine the mechanosensing role of angiotensin II type 1 receptor (AT1R) in flow-induced dilation (FID) and oxidative stress production in middle cerebral arteries (MCA) of Sprague-Dawley rats. Eleven-weeks old, healthy male Sprague-Dawley rats on a standard diet were given the AT1R blocker losartan (1 mg/mL) in drinking water (losartan group) or tap water (control group) ad libitum for 7 days. Blockade of AT1R attenuated FID and acetylcholine-induced dilations was compared to control group. Nitric oxide (NO) synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME) and cyclooxygenase inhibitor indomethacin (INDO) significantly reduced FID in control group. The attenuated FID in losartan group was further reduced by INDO only at ∆100 mmHg, whereas L-NAME had no effect. In losartan group, TEMPOL (a superoxide scavenger) restored dilatation, while TEMPOL+L-NAME together significantly reduced FID compared to restored dilatation with TEMPOL alone. Direct fluorescence measurements of NO and reactive oxygen species (ROS) production in MCA, in no-flow conditions revealed significantly reduced vascular NO levels with AT1R blockade compared to control group, while flow increased the NO and ROS production in losartan group and had no effect in control group. In losartan group, TEMPOL decreased ROS production in both no-flow and flow conditions. AT1R blockade elicited increased serum concentrations of AngII, 8-iso-PGF2α, and TBARS, and decreased antioxidant ...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Source Type: research