Absorption, Distribution and Endogenous Excretion of Zinc by Rats Fed Various Dietary Levels of Inorganic Tin and Zinc

Abstract

Three studies were designed to determine the effects of various levels of tin (<1, ∼100, ∼200, ∼500 and ∼2000 µg tin/g diet) and zinc (∼15, ∼30, ∼52 µg zinc/g diet) on the metabolism of zinc by growing rats. Retention of zinc in tibia, kidney, liver and plasma was decreased significantly when rats consumed ≥500 µg tin/g diet. Tibia zinc levels were also sensitive to lower levels of dietary tin, i.e., even 100 µg tin/g diet when rats were fed 51.8 µg zinc/g diet. Apparent absorption of zinc was significantly less when rats were fed ∼200 or ∼500 µg tin/g diet rather than a control diet containing 15.8 µg zinc/g diet and significantly less when rats were fed ∼500 µg tin/g diet rather than ∼200 µg tin/g diet with 29.7 µg zinc/g diet. The effect of dietary tin on fecal excretion of endogenous zinc and true absorption of zinc seemed to be dependent on the dose. Rats fed ∼2000 µg tin/g diet lost significantly more zinc of endogenous origin in the feces than control animals. A significant decrease in true absorption of zinc was observed among those rats fed ∼500 µg tin/g diet with 29.7 µg zinc/g diet. Increased consumption of zinc resulted in decreased apparent absorption of zinc, increased losses of endogenous zinc in the feces, and decreased true absorption of zinc.