Читать книгу Gas Biology Research in Clinical Practice - Группа авторов - Страница 36

Hydrogen sulfide (H₂S) is a colorless, toxic and flammable gas. It is a naturally occurring gas found in volcanic gases and some well waters and is also responsible for the foul odor of rotten eggs and flatulence. The toxic effects of H₂S in humans include eye irritation, shortness of breath, and chest tightness at concentrations <100 ppm. Exposure to H₂S at >1,000 ppm may cause severe adverse effects, ranging from loss of consciousness to fatality. H₂S is endogenously synthesized normally in vertebrates from L-cysteine, a product of food-derived methionine, by the cystathionone-β-synthase (CBS) and cyctathione-γ-lyase (CSE) system. The enterobacterial flora is another source of H₂S. H₂S is believed to help regulate body temperature and metabolic activity at physiological concentrations [12]. Also, H₂S exerts physiological effects in the cardiovascular system, possibly through modulation of K⁺-ATP channel opening or as a cellular messenger molecule involved in vascular flow regulation [13]. Administration of H₂S produced a ‘suspended animation-like’ metabolic status with hypothermia and reduced oxygen demand [14], thus protecting from lethal hypoxia. This hypometabolic state, which resembles hibernation, induced by H₂S may contribute to tolerance against oxidative stress. The effects of a soluble form of H₂S (using sodium sulfide) have been under investigation for clinical study on the patients who underwent coronary artery bypass graft (CABG) to potentially reduce the damage done to the heart during surgery.