Distribution and fate of 54Mn in the monkey: studies of different parts of the central nervous system and other organs

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Abstract
The fate and distribution of isotopic manganese administered as a single carrier-free dose of 200 μCi of maleate-54Mn to 12 rhesus monkeys was studied at different time periods from the 6th hr to the 278th day. Whole-body activity was measured, and all body organs and tissues and different parts of the central nervous system (CNS) were evaluated for specific activity, exponential analysis, and relative retention. Exponential analysis revealed a pattern of discharge with a fast and a slow component for the whole body and for many of the viscera. All parts of the CNS and, to a lesser degree, the thyroid and muscle showed an almost steady state of activity after the initial uptake. While the whole body and most organs and tissues appeared to discharge their radioactivity with the passage of time, first rapidly and then gradually, the CNS, endocrine glands, and muscle tissues showed persistent levels of specific activity. All components of the brain exhibited increasing relative retention, the lentiform nucleus and the cerebellum showing this more. It is suggested that the selective vulnerability of the brain in manganese miners might result from this inability on the part of the CNS to discharge the 54Mn with time. This investigation confirms and amplifies our earlier similar study on the rat.