Mammalian cyanide detoxification with sulphane sulphur

It has been understood for nearly a century that most of the cyanide entering mammals by either ingestion or inhalation of sublethal quantities is detoxified by combination with cyanide-reactive sulphur. The detoxifying reaction is primarily enzymic, and the enzymes that catalyse it, as well as those that catalyse reactions which generate the cyanide-reactive sulphane sulphur, have been isolated and studied extensively. However, analytical methods suitable for quantitative characterization of the physiological pool of sulphur available for this detoxification have only recently come under development. A new method is based on the evaluation of cyanide depletion under controlled, mild reaction conditions in the presence of a sulphurtransferase and cofactor. The use of differential pulse polarography with nested internal standards makes this a practical procedure for samples containing as little as a few nanomoles of cyanide-reactive material. As measured by this method, the sulphane sulphur concentration in mammalian liver tissue is in the fractional millimolar range, with even less in the bloodstream. Nevertheless, the specific binding of sulphane sulphur by serum albumin, and the rapid cyanolysis of the albumin-bound sulphur, may yet indicate a significant role for the sulphurtransferase capability of serum albumin in cyanide detoxification.