Chemical Status of Sulfur Dioxide in Water and Organic Solvents and Its Lipid/Water Partition Coefficient:A New Model for Physiological Study of Sulfur Dioxide

To explore chemical mechanisms of physiological and toxicological role caused by sulfur dioxide(SO2),chemical status of SO2 in water or two organic solvents were studied through analysis of SO2 concentration in solution containing SO2 before and after the solution to be treated by vacuum decompression,blowing nitrogen gas and ultrasonic treatment and so on.The saturation solubilities of SO2 in different solvents and its lipid/water partition coefficients(Kow)were also measured.Our results first demonstrated that 1)gaseous SO2 was easily dissolved in water,and much easily dissolved in organic solvents;2)Chemical status of SO2 in water or organic solvents was still an unchanged SO2 molecule;Percentages of the unchanged SO2 molecule in its saturated solutions for both water and organic solvents were more than 90%,and the percentages were about 50% in the solutions containing SO2 at lower concentrations;3)Kow of SO2 was only 0.16~0.20,suggesting endogenous SO2 was very easily entered into water phase from lipid phase in cells,and then it would be transferred to sulfite and bisulfite in weak alkaline body fluid,physiological activity of the latters was much weaker than that of SO2.Therefore,the half live of SO2 in tissues and cells was very short,it was accordant with characteristic of cell signal molecule.These results led to the conclusions:1)a new model for SO2 physiological and toxicological study could be established by exposure of SO2-bubbling saline asSO2 donorto biological tissues and cells in vivo or in vitro instead of SO2 gas.2)The un-activity pathway of SO2 in tissues and cells was SO2 →SO32-/HSO3-→ SO42-.Besides,it is indicated that mixture of sodium sulfite and bisulfite can not be used asSO2 donorto treat biological tissues.