The clearance of manganese chloride in the primate

The Clearance of Manganese Chloride in the Primate. NEWLAND, M. C., COX, C., HAMADA, R., OBERDÖRSTER, G., AND WEISS, B. (1987). Fundam. Appl Toxicol 9, 314-328. Two macaque monkeys inhaled trace amounts of ⁵⁴MnCl₂ for 30 min. Subsequently the chest, head, and fecal radioactivity were monitored for over a year. The chest data curve required a sum of three exponential terms, with half-times ranging from 0.2 to 187 days, to attain a satisfactory fit. Head levels peaked 40 days after acute inhalation exposure and remained elevated for over a year. The excretion of manganese through the feces was best described by a sum of two exponentials. One had a half-time of less than 1 day and the second had a half-time of 50 to 60 days. A third macaque received a 6-week continuous exposure to ⁵⁴Mn through a subcutaneous osmotic pump. With this route, manganese clearance from the head occurred at a faster rate than after acute inhalation exposure. Fecal elimination following continuous subcutaneous exposure resembled that following acute inhalation. Kinetic analyses suggested that the long half-times of manganese in the head following inhalation reflected both slow disappearance from the head and replenishment from other depots.