2.1. Renal artery preparation

Male Wistar rats (age 12–15 weeks) were euthanized by decapitation under light ether anesthesia. The renal artery was isolated carefully and transferred into a Petri dish containing oxygenated Krebs’ solution. The vessel was cut into ring segments of about 5 mm. The ring segments were mounted in baths containing 50 ml Krebs-Henseleit (KH) solution at pH 7.4. The composition of KH-solution is as follows (mM): NaCl (118.3), KCl (4.7), CaCl₂ (2.5), MgSO₄ (1.2), NaHCO₃ (25), KH₂PO₄ (1.2) and glucose (11.2). The tissue bath solution was maintained at 37°C and was aerated with 95% O₂/5%CO₂. Changes in vascular reactivity of the renal arteries were recorded by measurement of changes in the isometric tension to vasoactive agonists using computerized Automatic organ bath LSI Letica Scientific Instruments (Powerlab/8sp ADIinsturments, Panlab, Spain). A pre-tension of 0.5 g was applied and the preparations were allowed to stabilize (45 min) until a stable baseline tone was obtained. The integrity of the endothelial layer was tested before every experiment by testing the vasodilator response to carbachol (10⁻⁷ M). All studies involving animals were conducted in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals (NIH Publication number 85–23, Revised in 1985) as approved by Kuwait University Research Administration.