Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA349

Poster Communications

Angiotensin II type 1receptor antagonist losartan enhances vascular reactive oxygen species production in middle cerebral arteries of Sprague-Dawley male rats

I. Jukic1, Z. Mihaljevic1, A. Matic1, N. Kozina1, I. Drenjancevic1

1. Department of Physiology and Immunology, Faculty of Medicine J.J.Strossmayer University of Osijek, Osijek, Croatia.

Numerous studies provided the data that the renin-angiotensin system (RAS) is crtical for maintaining microvascular structure and vascular reactivity. The angiotensin II (ANG II) is the active end product of RAS that mediates its signal transduction and exerts it functions via ANGII receptors. Blockade of angiotensin II type 1 receptor (AT1R) signaling contributes to impairment of vascular reactivity to various vasodilator stimuli; however, the mechanism is not clear (1-3). Suppression of ANG II levels with high salt diet leads to increased vascular oxidative stress (4, 5). Present study aimed to determine the effects of AT1R antagonist losartan on vascular reactive oxygen species production (ROS) and level of vascular oxidative stress in middle cerebral arteries of rat. 11 weeks old healthy male Sprague-Dawley rats (n=17) were divided to a control (LS, n=6) and LS+Losartan group (n=11), both fed with standard rat chow with 0,4% NaCl, while rats from LS+Losartan group received 40 mg of Losartan (daily dose) in drinking water for 7 days. On the 8th day, prior to decapitation with a guillotine, rats were weighed and anesthetized with intraperitoneal injection of ketamine (75 mg/kg) and midazolam (2.5 mg/kg). Middle cerebral arteries were isolated and cannulated on pressure myograph, under flow (Δ80 mmHg) or no flow conditions, and in the absence / presence of TEMPOL (superoxide scavenger,100μM final concentration) in vitro. ROS production was determined by DHE (dihydroethidine) fluorescence measurements on Zeiss Axioskop MOT2 microscope with Olympus DP70 camera using a Zeiss filter set 15 with 546-nm wavelength for excitation and a 590-nm wavelength for emission with beam splitter at 580nm. Images were processed and analyzed withImageJ software. All experimental procedures conformed to the European Guidelines for the Care and Use of Laboratory Animals (directive 86/609) and were approved by institutional Ethical Committee. Flow-induced vascular ROS production was significantly increased in LS+Losartan group compared to LS group (p=0.0023), while in the absence of flow, ROS productions were similar between experimental groups. TEMPOL in vitro in LS+Losartan group significantly decreased vascular ROS production compared to LS+Losartan in the absence of TEMPOL [flow (p=0.004) and no flow (p=0.0012) conditions], and restored ROS to basal values compared to LS group in flow conditions. AT1R antagonist losartan enhances flow-induced vascular ROS production in the middle cerebral arteries of Sprague-Dawley rats. Since superoxide scavenging by TEMPOL restores reactive oxygen species production to control levels, results suggest increased level of vascular oxidative stress due to AT-1 receptor blocking.

Where applicable, experiments conform with Society ethical requirements