Fetal Uptake of ^<60>CoCl_2 and ^<57>Co-cyanocobalamin in Different Gestation Stages of Rats

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Fetal uptake of ^<60>CoCl_2 and ^<57>Co-cyanocobalamin was investigated in different gestation stages of rats. The fetal uptake of ^<60>CoCl_2 24 hrs after administration to pregnant rat slightly increased with the progress of gestation age at the administration but taking account of the growth of the fetus the value expressed in terms of concentration of ^<60>Co 24 hrs after injection decreased on the contrary. In the case of ^<57>Co-cyanocobalamin the fetal uptake 24 hrs after admlnistration to pregnant rat increased markedly when the time of injection was in later stag of pregnancy. Fetal accumulatlon of ^<57>Co-cyanocobalamin increased with time after injection and the retrograde transfer from fetus to mother was not observed. The amount of ^<57>Co-cyanocobalamin in the placenta is the greatest immediately after adminlstration followed by a gradual decrease thereafter. Since the amount of radiocobalt transferred through placenta in both chemical forms is greater than that accumulated in placenta, thls organ does not seem to play a role as a barrier to both forms of radiocobalt. It was observed that 1-2% of maternal dose of ^<57>Co-cyanocobalamln were transferred to sucklings via milk. The amount of milk-born cyanocobalamin in sucklings is dependent on the gestation age at the time of dosing.
日本放射線影響学会の論文