| The aim of this study was to investigate the effects of different extracellular K+ or Mg2+ concentrations ([K+] or [Mg2+] )on drug-induced vasoactive reactions among human isolated saphenous veins(HSV) and its possible clinical significances.The discarded distal ends of HSV were obtained from patients undergoing coronary artery bypass graft(CABG) surgery and isolated vascular ring models were prepared. The HSV rings were suspended between two stainless steel hooks in organ chambers and vascular tensions were recorded by a medlab biological signal collection system. Vascular strips of HSV were divided into four groups randomly: group I(2.7mM) , group II(4.7mM) , group III(6.7mM) , group IV(8.7mM) according to [K+] or group I(0.2mM), group II(0.6mM), group III(1.2mM), group IV(1.8mM) according to [Mg2+]. Experiment drugs comprised norepinephrine(NE, α -adrenergic receptor agonist, at concentrations of 0.6 × 10-9M, 0.6× 10-8M.,0.6× 10-7M, 0.6× 10-6M, 0.6× 10-5M and 0.6× 10-4M), dopamine(DA, vasodilation via an DA-recptor simulation at small concentrations, vasoconstriction via an a -adrenergic receptor stimulation at large concentrations, at concentrations of 10-9M, 10-8M, 10-7M, 10-6M, 10-5M and 10-4M), nitroglycerin(NTG, cGMP dependent, NO-donor drug , organic nitrate, at concentrations of 10-9M, 10-8M, 10-7M, 10-6M,10-5M and 10-4M), sodium nitroprusside (SNP, cGMP dependent, NO-donor drug ,endothelium independent, at concentrations of 10-9M, 10-8M, 10-7M, 10-6M, 10-5M and 10-4M) and acetylcholine(ACh, endothelium dependent vasodilation, endothelium independent vasoconstirction, at concentrations of 10-9M, 10-8M, 10-7M, 10-6M,...
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