Effects of chelating on organ distribution and excretion of manganese after inhalation exposure to 54MnCl2. II: Inhalation of chelating agents.

The effect of 1, 2-cyclohexylene-aminetetraacetic acid (CDTA) and diethylenetriaminepentaacetic acid (DTPA) on Min distribution and excretion in rats was examined after 1 hr exposure to 54MnCl2 (0.3 micrograms Mn/m3). Both chelating agents were inhaled independently, by nose only, for 30 min for the four following days, starting immediately after cessation of Mn exposure. During the experiment, the mean concentrations of CDTA and DTPA aerosols were 508 mg/cm3 and 517 mg/cm3, respectively. The activity of 54Mn was determined in lung, liver, kidney and brain 24 hrs after the last treatment, and in urine and faeces collected for 24 hrs on days 1-4 after Mn exposure. The CDTA inhalation appeared to be more effective than DTPA in mobilizing the inhaled manganese: about a twofold decrease of 54Mn was observed in all excised organs: lung, liver, kidney and brain, as compared to the controls. The DTPA inhalation resulted in about a twofold decrease of 54Mn in the lung, but was not effective in removing the metal from the liver, kidney and brain. As it can be seen from the comparison of these results with our previous data (6), the CDTA inhalations were more effective than its i.p. injections mobilizing manganese additionally also from the lung; but generally less effective in the case of DTPA, which decreased 54Mn levels in the lung only. On the first day after 54Mn exposure, manganese levels in the urine of rats inhaling CDTA and DTPA were respectively more than 200 and 30 times higher than in the control group. Excretion of Mn in faeces was not affected significantly in this experiment. Our data show that the effectiveness of removing inhaled Mn depends not only on the chelating agent, the time of its administration (see Part I) but also on the method of its administration.