Zinc deficiency, erythrocyte production, and chromosomal damage in pregnant rats and their fetuses

Association of Zinc with Anemia

Zinc is an essential trace element, and anemia is the most common blood disorder. The association of zinc with anemia may be divided into three major forms: (1) zinc deficiency contributing to anemia, (2) excess intake of zinc leading to anemia, and (3) anemia leading to abnormal blood-zinc levels in the body. In most cases, zinc deficiency coexists with iron deficiency, especially in pregnant women and preschool-age children. To a lesser extent, zinc deficiency may cooperate with other factors to lead to anemia. It seems that zinc deficiency alone does not result in anemia and that it may need to cooperate with other factors to lead to anemia. Excess intake of zinc is rare. However, excess intake of zinc interferes with the uptake of copper and results in copper deficiency that leads to anemia. Animal model studies indicate that in anemia, zinc is redistributed from plasma and bones to the bone marrow to produce new red blood cells. Inadequate zinc status (zinc deficiency or excess) could have effects on anemia; at the same time, anemia could render abnormal zinc status in the body. In handling anemia, zinc status needs to be observed carefully, and supplementation with zinc may have preventive and curative effects.

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).

Zinc Supplementation Stimulates Red Blood Cell Formation in Rats

In rats, mice, and humans, it is known that zinc deficiency may be related to anemia, and zinc supplementation influences hemoglobin production. Our previous studies indicate that in fish, zinc supplementation stimulates red blood cell (RBC) formation (erythropoiesis). However, it is not clear whether the mechanism of zinc-induced erythropoiesis stimulation in fish also occurs in rats. We induced anemia in rats using phenylhydrazine (PHZ) and injected either saline or ZnSO₄ solution. We found that an appropriate amount of zinc stimulated erythropoiesis in the PHZ-induced anemic rats. The effects of ZnSO₄ injection were dose-dependent. When the concentration of ZnSO₄ was higher than 2.8 mg zinc/kg body weight, the RBC level of the anemic rats increased from 60 ± 7% to 88 ± 10% that of the normal rats in two days. Rat bone marrow cells with or without ZnCl₂ supplementation were cultured in suspension in vitro. In the cell culture when the zinc concentration was at 0.3 mM, a 1.6-fold proliferation of nascent immature reticulocytes (new RBCs) was observed after one day. In the rat blood, zinc was combined with serum transferrin to induce erythropoiesis. The stimulation of RBC formation by zinc appears to be common among different animals.