Effect of Internal Exposure by 90Sr and 131I on Respiratory 14CO2 Patterns following 14C-Glucose Administration in Mice

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Abstract
Effects of internal irradiation by 90Sr and 131I were compared using 14C-glucose oxidation test in mice. Mice were injected with 2 μCi/g body weight of 90Sr or 5 μCi/capita of 131I for internal irradiation. At one day or 1, 3, 6, 9 weeks after injection of 90Sr and one or seven days after injection of 131I, the respiratory 14CO2 patterns of the animals were studied by continuous measurement of 14CO, and CO, in the exhaled air. The time course pattern of specific activity was obtained by calculating the ratios of the observed value of 14CO2 and CO2. The effect of internal exposure on respiratory 14CO2 were evaluated by the following parameters; 1) peak time, i. e., the time from injection to maximum specific activity, and 2) peak height, the maximum specific activity at peak time. In the control group, the value of specific activity of exhaled 14CO2 increased immediately after 14C-glucose administration, reached the maximum at 30 minutes and then gradually decreased. Internal irradiation with 90Sr caused a front shift, i. e., decrease in peak time with no appreciable change in peak height as compared with control. In the case of 131I, the respiratory pattern underwent an upper shift, i, e., increase in peak height with no change in peak time. To clarify the mechanism of the phenomena obtained by these internal emitters, the effect of some drugs on the change of respiratory 14CO2 pattern were studied. It was suggested that respiratory 14CO2 pattern analysis may serve as a useful tool in the comparative study of the effect of various internal emitters.

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