Investigation of Response to Angiotensin (Ang ) and its Receptor Subtypes in Acutely Inflamed Joint Blood Vessels in Rabbit

Introduction: Inflammatory joint diseases are common in elderly, and regulation of joint blood flow (JBF) is important in these conditions. The aim of this study was to investigate the response of inflamed joint blood vessels to angiotensin (Ang ), a vasoconstrictor factor which has been shown to be produced in inflamed joints locally. Identification of Ang receptor subtypes in joint blood vessels was the second goal of this study. Methods: The present study was performed on 12 Newzland white rabbits. Acute knee joint inflammation was produced by intraarticular injection of 0.5 ml of a 2% of carrageenan solution 24 hours before the experiment. On experiment day, animals were anaesthetized by thiopental sodium (50mg/kg ip) and carotid artery was cannulated for recording blood pressure. JBF was recorded by laser Doppler flow meter. Joint vascular resistance (JVR) was calculated by dividing arterial blood pressure by JBF. Results: Based on Ang dose/ response curve of joint blood vessels, the constrictor response was started from 10-12 M and reached to maximum at 10-5 M.Losartan completely inhibited this response with no vasodilation left behind, therefore the receptor subtypes are AT1. No evidence of presence of AT2 receptor subtype was observed in joint blood vessels. Conclusion: The comparison of the results of this study with a previous study on normal joints showed that the Ang receptor subtypes did not change due to the process of acute inflammation.