Abstract
The experiment that the recently identified vitamin "Thioctic Acid (TA)" (Lipoic Acid) and especially its reduced form "dihydro-TA" reacted with Hg to form an insoluble compound in vitro, and the evaluation of its antidotal capacities in vivo were already presented in the reports of Ueda, Ishii et al. in details. In the present report, the tracer experiment using Thioctic Acid labelled with S35 was conducted in order to find the distribution and excretion both in normal and mercury posioned state. If the excretion of TA is retarded in the case of mercury poisoning, either the damage of the kidney or the possibility of combining with Hg to form insoluble compounds and to be retained in the tissues may be expected. Animals used in this study were albino male rats of 140-250 g in body weight. TA and HgCl2 were simultaneously injected intramuscularly, each at the different side of the back. Each injected dose of TA was 40 mg/kg in the first experiment when given alone, or 23 mg/kg, equivalent to 30 mg/kg of HgCl2, when given simultaneously with HgCl2. The radio-activity of S35-TA was measured in samples extracted from autoclaved tissues by hexane. The results were as follows. 1) Distribution of S35-TA in the body of normal rats. S35-TA was distributed largely to the liver and small and large intestines. It reached the maximum level in the organs from 30 to 60 minutes following the injection, then decreased. But the excretion in the urine increased after 6 hours and kept that high level during 24 hours. 2) Changes in the dstribution of S35-TA by the administration of HgCl2. As shown in Table 3, radioactivities in the liver and the blood of the Hg treated group much increased in 30 minutes after the injection, compared with those of the control group, and still considerable amount of S35-TA remained even at 12th and 24th hour after the injection, whereas a remarkable decrease was observed in the controls by that time. The reason for this trend of retention might be explained that S35-TA combined with Hg is also highly distributed in these organs and forms an insoluble compound therewith.
