Effects of Thiosulfydryl Substances on the Metabolism of Heavy Metals

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Heavy metals taken into the tissues are transported among organs and are excreated out of the body sooner or later. In our previous studies, it was found that thiosulfydryl substances would play an important role in decreasing toxicity of heavy metals and eliminating metal concerned from the body. Thiocysteamine (TC), S-acetyl thiocysteamine (ATC) and thiotaurine (TT) were newly synthesized to investigate their detoxication effects on Methylmercury (MM) or Cd metabolism in tissues and urine.1. In vitro experiments; TC could libelate 40 to 90% of MM from the tissues pre-treated with MM, and MM added was also released from the tissues pre-incubated with TC. However, in the later experiment, the releasing effect diminished after pre-incubation for 100 min. As for Cd, observing Cd concrntration ratio of supernatant to residue and Cd contents in protein fractions in the liver preloaded with Cd, any changes were not found.2. In vivo experiments; The drugs were administered under the different conditions to mice pretreated with MM. The contents of mercury slightly increased in urine and decreased in kidney after the administration of TC alone, but no progression of mercury elimination was observed even in TC administration mixed wiyh either glutathione, cysteamine or Intrafat. ATC and TT did not reveal any effects. The significant effects on Cd movement in tissues were not recognized in case of the administration of TC to mice pretreated with Cd.Thus, only TC in thiosulfydryl substances newly synthesized manifested the effect on MM metabolism in vitro experiments, but even TC did not have the intended effect in vivo experiments. For this reason, one cause is that the drugs were chemically unstable, so it is necessary to introduce alkyl terminal instead of H-terminal in -S-S-H radical of thiosulfydryl substance. The further study should be continued in the future.