Decrease of the responsiveness of beta-2 adrenoceptors of diabetic rat knee joint blood vessels in acute inflammation

Beta-2 adrenoceptors in blood vessels are one of the active factors that play a role in regulation of tissue blood flow. in diabetic angiopathy, responsiveness of these receptors is decreased, while that is increased in inflammation. According to these opposite effects, the aim of this study was to investigate the vasodilatory response of knee joint blood vessels to salbutamol (Beta-2 adrenoceptor agonist) in IDDM with combination of acute inflammation. Acute knee joint inflammation was induced by intraarticular injection of kaolin 4% and induction of diabetes was performed by streptozotocine (55 mg/kg). Wistar rats weighting 200-300 gr were used. The animals divided in 5 groups as: the control, saline, diabetic, inflammatory and diabetic- inflammatory. Blood flow of knee joint was measured using Laser Doppler Flowmeter Technique (LDF). Vasodilatation of articular micro vascular was measured in response to topical application of different concentration (10 -11 -10 -1) of salbutamol. Results obtained in this study showed that: 1- Increased knee joint diameter and perimeter due to acute inflammation in diabetic rat knee joint were significantly lesser than that of inflammatory rats. 2- Responsiveness of Beta-2 adrenoceptors were increased in kaolin- induced acute inflammation. 3- In diabetic rats, kaolin- induced acute inflammation could not increase the responsiveness of Beta-2 adrenoceptors. Based on above mentioned results, we conclude that diabetes inhibits the increasing effects of acute inflammation on responsiveness of Beta-2 adrenoceptors.