METALLOTHIONEIN EXPRESSION IS INCREASED IN MONOCYTES AND ERYTHROCYTESOF YOUNG MEN DURING ZINC SUPPLEMENTATION

The metallothionein gene is transcriptionally regulated by zinc. Conse quently, metallothionein has potential for serving as an index of diet ary zinc status in humans. To examine this possibility, an enzyme-link ed immunoassay (ELISA) based on a sandwich approach that utilizes mono clonal and chicken egg yolk antibodies was used to compare the respons e of erythrocyte metallothionein protein levels with the response of m onocyte metallothionein mRNA levels as measured by competitive reverse transcriptase-polymerase chain reaction (CRT-PCR) during zinc supplem entation. Young male subjects participated in an 18-d supplementation study in which zinc was provided at 50 mg/d. Control subjects received a placebo. The zinc supplement resulted in significantly greater eryt hrocyte metallothionein levels by d 8 of supplementation compared with controls, Monocyte metallothionein mRNA levels were significantly gre ater than those of controls by d 2 of supplementation. Both remained e levated through d 18. They returned to base line by 8 and 4 d after su pplementation, respectively. The plasma zinc concentration was signifi cantly greater than in controls by d 6 and had returned to control lev els by d 22 of supplementation. The results presented here show that b oth monocyte metallothionein mRNA and erythrocyte metallothionein prot ein concentrations change in human subjects in response to elevated di etary zinc intake and that monocyte metallothionein mRNA responds more rapidly to elevation of dietary zinc status than erythrocyte metallot hionein protein. Consequently, both erythrocyte metallothionein and mo nocyte metallothionein mRNA may prove to be measures useful for assess ment of either zinc depletion or the bioavailability of zinc supplemen ts.