Cobalt - trace element, nutritional supplement and regulator of hematopoiesis

Cobalt (II) is a wide used metal as erythropoietic agent, nutritional supplement, in cosmetics, medical devices. The aim of the study was to evaluate the regulatory role of chronic treatment with cobalt compounds on mouse hematopoiesis. An in vivo experimental model for chronic exposure to cobalt chloride (CoCl2) and/or cobalt-EDTA (Co-EDTA) was established. Pregnant ICR mice were subjected to daily dose of 75 and/or 125 mg/kg body weight CoCl2x6H2O and/or Co-EDTA 2-3 days prior delivery. The compounds were dissolved in tap water. 25 pn newborn mice were separated into individual cages and treatment continued until day 90 pn. The animals were sacrificed on days 18, 25, 30, 45, 60 and 90. The control group consisted of age-matched mice obtaining tap water. Co(II) accumulation was analyzed in blood plasma and tissues. Whole blood was used for hematological analyses and histological studies were performed to evaluate the morphological changes. Results showed diverse effect of Co(II) compounds on immature and mature mice. Analysis of whole blood samples demostrated that immature mice (days 18 to 30) show signs of anemia determined by reduced RBC and hemoglobin (Hb) content. Hb was significantly increased in mature (day 45 to 90) mice suggesting time- and age-dependent effect of the compounds. More Hb was measured in samples of mice exposed to the higher dose (125 mg/kg), indicating a dose-dependent effect as well. CoCl2 exhibited stronger stimulatory effect compared to Co-EDTA. The results correspond to higher concentrations of Co(II) in the plasma of immature mice, compared to the mature ones.Exposure to cobalt ions affected megakaryocyte formation. In the spleen, CoCl2 stimulated megakaryocyte formation while Co-EDTA inhibited it.Results suggest that the regulatory role of cobalt on hematopoiesis depends on the type of compound, the duration of treatment, as well as on the age of the experimental animals.