SUMMARY Since the 1980 s nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S), the endogenous gas molecules produced from metabolic pathway, have been realized as signal molecules to be involved in the regulation of body homeostasis and to play important roles under physiological and pathophysiological conditions. The researches on these endogenous gas signal molecules opened a new avenue in life science. To explore the new member of gasotransmitter family, other endogenous gas molecules which have been regarded as metabolic waste up to date, and their biological regulatory effects have been paid close attention to in the current fields of life science and medicine. Sulfur dioxide (SO2) can be produced endogenously from normal metabolism of sulfur-containing amino acids. L-cysteine is oxidized via cysteine dioxygenase to L-cysteinesulfinate, and the latter can proceed through transamination by glutamate oxaloacetate transaminase (GOT) to β-sulfinylpyruvate which decomposes spontaneously to pyruvate and SO2. In mammals, activated neutrophils by oxidative stress can convert H2S to sulfite through a reduced form of nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase-dependent process. The authors detected endogenous production of SO2 in all cardiovascular tissues, including in heart, aorta, pulmonary artery, mesenteric artery, renal artery, tail artery and the plasma SO2 content. As the key enzyme producing SO2, GOT mRNA in cardiovascular system was detected and found to be located enrichedly in endothelial cells and vascular smooth muscle cells near the endothelial layer.When the normal rats were treated with hydroxamate(HDX), a GOT inhibitor, at a dose of 3.7 mg/kg body weight, the blood pressure (BP) went high markedly, the ratio of wall thickness to lumen radius was increased by 18.34%, and smooth muscle cell proliferation was enhanced. The plasma SO2 level in the rats injected with 125 μmol/kg body weight SO2 donor was increased to 721.98±30.11 μmol/L at the end of 30 seconds, while th
