Investigation of the Response of Vascular Alpha1- Adrenergic Receptors of Diabetic Rat Knee Joint in Acute Inflammation

Alpha 1–adrenoceptors in blood vessels are one of the active factors that plays a role in regulation of tissue blood flow. In diabetic angiopathy, responsiveness of these receptors is increased, while that is decreased in inflammation. According to these opposite effects, the aim of this study was to investigate the vasoconstrictor response of knee joint blood vessels in IDDM with combination of acute inflammation. Acute knee joint inflammation was induced by intraarticular injection of kaolin 3% - carrageenan 3% suspension and induction of diabetes was done by intravenous injection of alloxan (70mg/kg). Albino rats weighing 70-90 g were used. The animals divided into four groups as: control, diabetic, inflammatory and diabetic – inflammatory. Blood flow of knee joint was measured using laser doppler flowmeter (LDF). Vasoconstriction of joint was measured in response to topical application of different concentrations (10-7-10-3 M) of phenylephrine. Results obtained from this study showed that: 1- Increased knee joint diameter and circumference due to acute inflammation in diabetic rat knee joint was significantly lower than control rats. 2- Knee joint basal blood flow in diabetic rats was significantly lower than control rats. 3- The responsiveness of alpha1-adrenoceptors decreased in kaolin-carrageenan induced inflammation. 4- In diabetic rats kaolin-carrageenan induced inflammation could not decrease the responsiveness of alpha1- adrenoceptors. Based on the above mentioned results, we conclude that diabetes inhibits the reductive effects of acute inflammation on responsiveness to alpha1-adrenoceptors. The exact mechanisms involved in this phenomenon are remain to be revealed.