Increased retention of orally administered zinc and raised blood cell zinc concentrations in iron-deficient rats.

I. Rats were made severely iron-deficient by feeding with Fe-deficient diets, which contained adequate amounts of zinc. 2. Ten days after an oral dose of 250 ,ug %n the Fe-deficient rats had retained 17 yo whereas control rats had retained only 8 yo of the dose. 3. When unlabelled Zn was given intravenously to the Fe-deficient and control rats there was a reduction in retention of the orally administered W n . This effect was not produced when Fe was given before the oral dose of 65Zn. 4. Total body Zn, whole blood Zn and plasma Zn concentrations of the rats were measured by atomic absorption spectrophotometry. Both the Fe-deficient rats and the control rats had the same total body Zn calculated as a proportion of body-weight. The plasma Zn concentrations were normal in all the animals. Blood cell Zn concentrations in the Fe-deficient animals were raised. 5 . The blood cell Zn concentration was directly related to the reticulocyte count in all the rats. 6. It was concluded that Fe and Zn are absorbed by different metabolic pathways, and that there is an increased turnover of Zn in the Fe-deficient rats, possibly related to the short lifespan and increased Zn concentration of Fe-deficient rat erythrocytes. In the rat abnormalities of Zn concentration can only be considered significant if Fe status is also known.