Methemoglobin Formation in Human Blood by Cobalt IN VITRO1

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Abstract
Formation by methemoglobin was quantitated when normal human erythrocytes were incubated in serum for 24 hours at 37[degree]C with cobaltous chloride and/or various oxidizing and reducing agents. Methemoglobin production by cobaltous chloride alone was regarded as due to failure of the normal cellular reducing mechanism rather than to acceleration of an oxidative process. Thus, methemoglobin formation by p-aminophenol was marked within 6, but by Co only after 24 hours; and anoxic conditions decreased this action of the former but not of the latter chemical. This implies that Co does not produce methemoglobin by the same mechanism as does p-aminophenol, a substance known to oxidize hemoglobin directly. Methylene blue, which in appropriate amounts catalyzes the enzyme system of the red cells responsible for the reduction of methemoglobin, inhibited the methemoglobin-form ing action of p-aminophenol but not of Co. Ascorbic acid, an agent known to reduce methemoglobin directly, reconverted methemoglobin formed both by Co and by p-aminophenol. When hemoglobin was purified and the cellular enzymatic reducing mechanism was no longer present, no appreciably greater amount of methemoglobin was formed by Co than by an inert substance, NaCl. It is well known that anoxia of arterial blood or administration of Co to normal animals or man results in polycythemia. With Co there is no methemoglobin formation or decrease in the O2 capacity of peripheral blood. Consequently, the physiological relevance of the authors'' observations to erythropoiesis is not direct. However, the experiments are at least consistent with the hypothesis that Co by interfering with cellular reducing systems might induce anoxia of tissues, including those controlling erythropoiesis, and thus might stimulate erythropoiesis.