Mechanism Of The Cardiovascular System Of SWNTs In Rats

Effect of SWNTs on sodium current in rat ventricular myocytesAIM: To study the effect of SWNTs on sodium current in SD rats ventricular myocytes, and explore the possible mechanisms underlying them.METHODS: the whole-cell patch-clamp techniques were used to record INa in isolated ventricular myocytes from SD rats. Effects of SWNTs(Respectly) on ventricular myocytes.RESULTSL: SWNTs increased the amplitude of whole cell INa by concentration -dependent manner. 0.01mg/ml SWNTs activted INa by (12.34±3.56)%,0.03 mg/ml SWNTs activted INa by (31.45±4.25)%,0.1 mg/mlSWNTs activted INa by (52.36± 4.56)% ( n = 8,respectly) .CONCLUSION: SWNTs decreased the amplitude of whole cell INa by concentration -dependent manner. This results the mechanism of arrhythmia. Mechanism of the vasoconstriction of SWNTs on excised thoracic aorta annulations in ratsObjective:It is to study the function of SWNTs on the contraction tension of excise thoracic aorta annulations in rats and its possible pathway. And it is to study Pathophysiologic morphology of thoracic aorta by electron microscope.Methods:Isometric tension was recorded in response to drugs in organ bath. Effects of SWNTs (25μg/ml; 50μg/ml;100μg/ml respectively ) on the vascular tone of resting, noreinephrine(NE)( 1μmol/ L) pre - constricted rat thoracic aorta with or without endothelium were determined. The tension was recorded in calcium-free Krebs solution. To explore the mechanism, nitric oxide synthase inhibitor L - N( G) - nitroarginine methyl ester (L - NAME) (10μmol/ L) , capsazepine (10μmol/L), Phentolamine(10μmol/L), Nifedipine (10μmol/L) were used.Results: The three concentrations of SWNTs produced constriction in both endothelium-intact and endothelium-denuded rings. Constriction of endothelium-denuded rings was more than that of endothelium-intact rings(p<0.05). SWNTs caused concentration -independent relaxation of aorta rings preconstricted with PE (1μmol/ L) in endothelium–intact and endothelium-denuded rings. Nifedipine,metoprolol and capsazine inhibited the contractile effect of SWNTs on the rat thoracic aorta rings, but the effect of phentolamine on the vasoconstriction of SWNTs was not observed. SD rats were randomizdly divided into the control group and the experimental group. The experimental animal modle was established by the direct tracheal instillation of SWNTs into rate lungs surgically. The control rats underwent directly tracheal instillation of saline into lungs surgically, and no surgical group. Ten rats from each group were sacrificed at twelfth or thirteenth week, and removed aortic. The tissue of the model rats was determined by immunohistochemistry.Conclusion:The results indicate that the contraction by SWNTs in rat aorta ring is possibly mediated by the Ca2+ channels, TRPV1 receptors andαreception pathway; The relaxation by SWNTs is endothelium dependent and possibly mediated by the Nitric Oxide-guanylyl cyclase pathway; such SWNTs had no effect of morphology.