ABSTRACT
Objective To investigate the vasorelaxant effect and possible mechanism of niclosamide ethanolamine (NEN)on isolated rat coronary artery(RCA). Methods Wire myograph was used to record myogenic tone of vessels. The vasorelaxant effect of NEN was studied in RCA precontracted with either KCl or U46619. Study of related inhibitors was performed to investigate possible involvement of potassium channels and the mitogen-activated protein kinase(MAPK) signaling pathway in vasorelaxation. The effect of NEN on Ca2+mobilization was determined by observing vasoconstrictor-induced contractions in tissue solution deprived of Ca2+followed by Ca2+restoration. Results NEN(0.5-3.0 μmol/L) relaxed RCA precontracted with KCl or U46619 in a concentration-dependent manner. MAPK inhibitors(PD98059 and SB239063)reduced the relaxant effect of NEN,while the potassium-channel blockers(tetraethylamine,4-aminopyridine, BaCl2,and glibenclamide)did not significantly affect relaxation. NEN specifically inhibited the contraction component dependent on extracellular Ca2+influx in vessels stimulated with KCl and U46619, with a negligible effect on the component dependent on intracellular Ca2+release. Conclusions NEN exhibits vasodilator properties in RCA. Inhibition of extracellular Ca2+influx and activation of the MAPK signaling pathway may be involved in NEN-induced RCA vasorelaxation.
ABSTRACT
AIM:To explore the mechanisms underlying contraction induced by extracelluar acidosis (pHex6.8) in rat isolated coronary artery (RCA).METHODS:Using the microvessel tension recorder system, the effects of acid-base transporters on RCA contraction induced by pHex6.8 were explored by applying the selective pharmacological inhibitors of Na+-H+ exchanger 1 (NHE-1) and Na+-HCO-3 cotransporter (NBC), HOE-642 and S0859, respectively.The effects of chloride channel on RCA contraction induced by pHex6.8 were explored by applying the inhibitors of chloride channel (NPPB and NFA), and by replacing the extracellular NaCl with equimolar NaBr.RESULTS:pHex6.8 augmented the resting tension of RCA, and the maximum contraction was (3.90±0.95) mN.HOE-642 at 30 μmol/L and S0859 at 100 μmol/L both inhibited the contraction of RCA induced by pHex6.8 (P<0.01).NPPB and NFA both inhibited the contraction of RCA induced by pHex6.8 or KCl (60 mmol/L) in a concentration-dependent manner.NPPB and NFA (100 μmol/L) both inhibited the contraction of RCA induced by U46619 (1 μmol/L).Replacing the extracellular NaCl with equimolar NaBr almost completely inhibited RCA contraction induced by pHex6.8 (P<0.01), but had no obvious effect on the contraction induced by KCl (60 mmol/L) or U46619 (1 μmol/L).CONCLUSION:Extracellular acidosis-induced contraction in RCA may be related to the activated NHE-1 and NBC, and it may be also related to the enhanced chloride transport across the membrane.