ZINC-METABOLISM AND METALLOTHIONEIN EXPRESSION IN BONE-MARROW DURING ERYTHROPOIESIS

Zinc metabolism and metallothionein induction in rat bone marrow were investigated during induced erythropoiesis. Redistribution of body zinc was measured with Zn-65 after acute blood loss in rats fed zinc-restricted or zinc-adequate diets. Uptake of Zn-65 by bone marrow was related to time after blood loss, metallothionein induction, and dietary zinc status. Increased Zn-65 uptake by marrow of zinc-restricted rats suggests a minimal amount of zinc is necessary to support expansion of the erythrocytic compartment. Zinc induction of marrow metallothionein also occurred in rats in which anemia was produced using phenylhydrazine. Anemic rats which were administered zinc had higher concentrations of marrow metal-lothionein compared with control rats. Induction of marrow metallothionein by zinc in nonanemic rats required prior treatment with erythropoietin. Percoll fractionation showed marrow metallothionein was most abundant in erythroblasts. These experiments suggest metallothionein synthesis occurs in erythropoietin-sensitive precursor cells in the marrow in response to increased zinc accessibility.