Cyanide Antagonism with Carrier Erythrocytes and Organic Thiosulfonates

Abstract Cyanide Antagonism with Carrier Erythrocytes and Organic Thiosulfonates. Petrikovics, I., Cannon, E. P., McGuinn, W. D., Pei, L., Pu, L., Lindner, L. E., and Way, J. L. (1995). Fundam. Appl. Toxicol. 24, 86-93. Previous studies reported that resealed erythrocytes containing rhodanese (CRBC) and Na 2 S 2 O 3 rapidly metabolize cyanide to the less toxic thiocyanate both in vitro and in vivo. This provided a new conceptual approach to prevent and treat cyanide intoxication. Although the rhodanese-containing carrier cells with thiosulfate as the sulfur donor were efficacious, this approach has potential disadvantages, as thiosulfate has limited penetration of cell membrane and product inhibition of rhodanese can occur due to inorganic sulfite accumulation. In order to circumvent substrate limitation and product inhibition by sodium thiosulfate, organic thiosulfonates were explored. These thiosulfonates have higher lipid solubility than thiosulfate and therefore can replenish the depleted sulfur donor, as they can readily penetrate cell membranes. Also, product inhibition of rhodanese is less apt to occur. This change in sulfur donors should greatly enhance cyanide detoxication, replenish the sulfur donor, and minimize product inhibition of rhodanese. Present studies demonstrate the enhance efficacy of exogenous organic thiosulfonates over sodium thiosulfate in the CRBC antidotal system to detoxify the lethal effects of cyanide either alone or in combinations with exogenously administered NaNO 2 . Murine carrier erythrocytes containing purified bovine liver rhodanese were administered intravenously into male Balb/C mice. Subsequently, butanethiosulfonate (BTS) or Na 2 S 2 O 3 (ip), and NaNO 2 (sc) were co-administered prior to KCN (sc). Potency ratios, derived from the LD 50 values, were compared in groups of mice treated with CRBC-Na 2 S 2 O 3 or CRBC-BTS either alone or in combination with NaNO 2 . The CRBC-BTS antidotal system shows strikingly enhanced protective effect over that of the CRBC-thiosulfate system either alone or in combination with sodium nitrite.