EXPERIMENTAL STUDIES ON THE LATENT CARBON DISULFIDE INTOXICATION IN MICE, WITH SPECIAL REFERENCE TO THE RESPIRA TORY FUNCTION

It is likely that in the near future industrial physicians will have to deal with more and more cases of extremely slight intoxication without appropriate diagnostic means. Therefore, newer methods must be developed to detect the latent damages which have been overlooked by the conventional methods of examination. It was reported by several papers that the mice chronically exposed to CS2 died at higher death rate than the untreated mice when they were exposed secondarily to CS2 of higher concentrations. In these cases any signs of intoxication prior to the secondary exposure could not be found. This fact implies that the latent CS2 poisoning in mice could be detected by the secondary loading of CS2. To clarify the nature of the inapparent abnormality in these mice and to find some clues for establishing a new method to detect the latent CS2 intoxication in man, experiments were performed with the following results. (1) Mice exposed to 300 ppm CS2, eight hours a day, for 30 days did not show any signs of chronic CS2 poisoning, judged from the usual toxicological criteria such as growth rate, leucocyte count, hemoglobin concentration and histopathological findings of the lung, kidney, spleen, bone marrow and the brain. The respiratory rates of the exposed group, however, decreased much more rapidly than those of the control group, when the both groups were exposed secondarily to 3000 ppm CS2. (2) The above findings were ascertained more clearly when intraperitoneal injection, instead of inhalation, of CS2 was adopted as the route of administration. In this case, the respiratory rates of the exposed group decreased remarkably, and more than half of them died of respiratory paralysis, while those of the control group remained normal. (3) Moreover, intraperitoneal injections of some central nervous system depressants were tested on the assumption that these drugs, with their remarkable respiratory depressant action, could manifest the same effect as the administration of CS2. As anticipated, one of them, thiopental sodium, depressed definitely the respiratory rates of the exposed group and no depressions were found in the control group. (4) The latent CS2 intoxication in mice as detected with the above mentioned methods was found to be established by a 19-day exposure to 300 ppm CS2 and recovered by discontinuation of the exposure for 100 days. From these results, as well as from references, it was discussed and estimated that the inapparent abnormality in the latently CS2 poisoned mice was located at the respiratory center. This work suggests the possibility of finding some practical methods to detect the latent CS2 intoxication in man.