Effects of Taurine on Aortic Rings Isolated from Fructose-fed Insulin Resistance Sprague-Dawley Rat are Changed

To observe and compare the effect of taurine on contractions of aortic rings isolated from normal (NC) and insulin resistance (IR) Sprague-Dawley rats, and to explore its underlying mechanism(s). The IR animal model was made by feeding rats with high fructose diet for 8 weeks. Aortic rings were isolated and suspended in a tissue bath, and tensions were recorded isometrically. The effects of taurine on provoked contractions of the rings were assessed in absence or presence of different potassium channel or NO-synthase inhibitors. Taurine (20-80 mM) concentration-dependently relaxed precontractions induced by KCl (30 mM) and phenylephrine (1 mu M) in NC rings, but enhanced the precontractions in IR rings. Denudation of the endothelium and pretreatment with N G-nitro-l-arginine methylester ester (0.1 mM) reversed the contraction enhancement of taurine to relaxation in IR rings. Tetraethylammonium (10 mM) nearly abolished taurine-induced relaxation of NC rings, and augmented taurine-induced contraction enhancement in IR rings. Iberiotoxin (100 nM) only augmented the contraction enhancement in IR rings. 4-Aminopyridine (1 mM), glibenclamide (10 mu M) and indomethacin (10 mu M) had no influence on the effect of taurine in both NC and IR rings. Taurine enhances contractions in IR aortic rings but relaxes the contractions in normal rat aortic ring; the enhancement is endothelium-dependent and the relaxation is endothelium-independent. TEA-sensitive K+ channel may be involved in these actions; BKCa channel dysfunction and endothelium-derived substances may be related to the contraction enhancement induced by taurine in IR aorta.