Comparative Metabolism of Radionuclides in Mammals-III Retention of Manganese-54 in the Mouse, Rat, Monkey and Dog

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Abstract
Radiomanganese (54Mn) was administered to mice and rats by the oral, intravenous and intraperitoneal routes and to dogs and monkeys by the oral and intravenous routes. Whole-body-counting techniques, utilizing 4pi liquid scintillation counters, were used. to determine whole-body-retention parameters. Retention functions consisting of the sum of three or four exponential expressions were adequate descriptions of retention until the body burden was less than 1 per cent of the administered dose. The longest effective half times after intravenous injections were 119, 146, 99 and 68 days for mice, rats, monkeys and dogs, respectively. Tissue distribution studies in rats showed that, for most tissues, concentration as a function of time roughly paralleled whole-body retention. Both bone and brain were found to have a slower rate of loss than other tissues. Using a parabolic relation between body weights and the integrals of the retention functions, it was estimated that 6 × 10−3 μc/ml was the maximum permissible concentration in water when the total body is the critical organ. This value is in good agreement with the current ICRP value of 8 × 10−3. However, the value calculated for the lower large intestine (1 × 10−3 μc/ml) must remain the MPCw for 54Mn.