In anemia zinc is recruited from bone and plasma to produce new red blood cells

Anemia is highly prevalent in people with chronic kidney disease (CKD), and CKD patients always have lower plasma but higher erythrocyte Zn levels than healthy people. To date, no satisfactory mechanism has explained these Zn metabolism abnormalities. We collected blood samples from patients on hemodialysis, 5/6 nephrectomized rats and phenylhydrazine (PHZ)-induced anemic mice and rats and compared them with their normal counterparts. We found that all the anemic animals had significantly decreased plasma Zn levels but elevated erythrocyte Zn levels. We also found that in anemic mice, new red blood cells (reticulocytes) had a ~7-fold higher Zn concentration than mature erythrocytes. When excess Zn was supplied to the rats, there was a ~1.2-fold increase in the Zn level in the rat bones. When Zn was depleted in the rats, the bones lost the greatest amount of Zn in the body (a 45% decrease). We prepared Zn-depleted rats and rendered these rats anemic by treating them with PHZ, and we compared them with normal rats. We found that in PHZ-induced anemia, rats released ~16% of Zn from their bones. Rat bones not only act as a 'reservoir' to adjust the excess or deficient Zn levels but also release Zn in anemia, and the released Zn stimulates erythropoiesis in the bone marrow. In anemia, Zn is redistributed from the plasma (causing the plasma Zn level to decreases) and bones to the bone marrow to produce reticulocytes (causing erythrocyte Zn level elevation).