Zn-depleted mice absorb more of an intragastric Zn solution by a metallothionein-enhanced process than do Zn-replete mice

The influence of metallothionein (MT)(2) on Zn absorption was investigated in MT-null (MT-/-) and normal (MT+/+) mice fed Zn-depleted (ZnD) diets for 7 d and compared with those fed Zn-replete (ZnR) diets in a previous study. Mice were starved for 20 h, then administered an oral gavage of aqueous (Z nSO4)-Zn-65 solution at doses of 154, 770 or 1540 nmol of Zn, and the amoun t transferred into nongut tissues was determined 4 h later. Zn-65 transfer did not differ between genotypes in ZnR mice. However ZnD MT+/+ mice had a 30-40% greater transfer from the 154 and 770 Zn doses compared to ZnR MT+/ mice. This was not observed in MT-/- mice. In MT+/+ mice, Zn depletion enh anced the induction of MT by Zn in the intestine and pancreas. 65Zn uptakes in the liver and pancreas were greater in MT+/+ than MT-/- mice, and this was greater (50%) at the 154 and 770 doses in mice fed ZnD diets. Plasma Zn concentrations were raised to a similar extent in ZnR and ZnD MT-/-mice. Z nR MT+/+ mice had significantly lower plasma Zn levels than MT-/- mice; thi s difference was less marked in the ZnD mice. We conclude that a MT-facilit ated enhancement in Zn absorption occurs in response to dietary Zn deficien cy.