AIM To study the effects of DIDS and furosemide on the contraction induced by
phenylephrine and the endothelium-dependent
relexation induced by ATP. METHODS Measurement of isometric force of rat thoracic aortae rings with and without endothelium. RESULTS DIDS(1～300 μmol·L -1 ) and furosemide(10～320 μmol·L -1 ) inhibited the contractile response induced by
phenylephrine in a concentration-dependent manner. The inhibitory rate was different between aortic ring endothelium-intact and that endothelium-denuded. The values of IC_ 50 for DIDS were (12.0±8.0) μmol·L -1 and (28.3±7.3) μmol·L -1
respectively,while the values of IC_ 50 for furosemide were (17.9±6.6) μmol·L -1 and (41.0±15.6) μmol·L -1 respectively. DIDS(10 μmol·L -1 ) did not chang ATP-induced vasodilative effect at the concentrations of 10 μmol·L -1 and 100 μmol·L -1 , but enhanced the relaxation induced by 1 mmol·L -1 ATP. Furosemide (20 μmol·L -1 ) had no effect on the relaxation induced by ATP(10 μmol·L -1 ), but prolonged the relaxation when the concentration of ATP added to 100 μmol·L -1 and 1 mmol·L -1 ( P< 0.01). CONCLUSION Both DIDS and furosemide could inhibit the contraction induced by phenylephrine. The inhibitory rate in the aortic ring with endothelium was higher than that of no endothelium. These chloride channel blockers could increased the endothelium-dependent vasodilative response to ATP.