The vasodilator mechanisms of sodium metabisulfite on precontracted isolated aortic rings in rats: Signal transduction pathways and ion channels

摘要

Sodium metabisulfite (SMB) is most commonly used as a food additives, however few study was performed on the vasodilator effect of SMB. In the present paper, the vasodilator effects of SMB and roles of Ca 2+ and K + channels as well as the cGMP pathway on isolated rat aortic rings were studied. The results show that: (1) SMB could relax isolated aortic rings precontracted by norepinephrine in a concentration-dependent manner. The maximal endothelium-dependent vasorelaxation was approximately 20% whereas that not depending on the presence of the endothelium was more than 90%. (2) The vasorelaxant effects induced by 50 or 200μM SMB were partially inhibited by iberiotoxin, NS-2028 or l-NNA. The vasorelaxation of 1000μM SMB was partially inhibited by nifedipine or glibenclamide. The SMB induced vasorelaxation was partially inhibited by tetraethylammonium. These results led to the conclusions that the vasorelaxation of SMB at low concentrations (400μM) was endothelium-dependent and mediated by the cGMP pathway and BK Ca channel, but at high concentrations (500μM) was endothelium-independent and mediated by K ATP channel and L-type Ca 2+ channel. The maximal allowable concentration from China and the acceptable daily intake level from WHO of SMB as a food additive should be revised.