Age-dependent Variation of Zinc-65 Metabolism in LACA Mice

Summary

Mice were gavaged with zinc-65 solution, 8·6–19·3 kBq per mouse, and the whole-body retention and organ content of zinc-65 were measured at different times after administration. The age-dependence of the fractional absorption of zinc-65 from the gastrointesinal tract (f₁), the endogenous faecal excretion fraction of zinc-65 (EFEF), tissue distribution and whole-body retention were determined. The f₁ values obtained were 0·86 ± 0·15, 0·64 ± 0·11, 0·52 ± 0·07 and 0·39 ± 0·02 in suckling, adolescent, young adult and older mice, respectively. The EFEF values determined were 0·083 ± 0·008, 0·099 ± 0·004, 0·122 ± 0·018 and 0·144 ± 0·005 of intraperitoneally injected zinc-65 in suckling, adolescent, young adult and older mice at administration. Zinc-65 mainly distributed in the liver, muscle, lung, kidneys and bone. In some tissues, there was an inverse relationship between the relative content of gavaged zinc-65 and the animal's age at administration. The whole-body biological half-lives of zinc-65 increased with animal age. The influence of the age-dependent variation of zinc-65 metabolism on internal dose and on radiation protection is discussed.