Does Methylene Blue Form Methemoglobin?

Abstract

These experiments were done to help clear up the present confusion as to the action of methylene blue on hemoglobin.

Barron and Harrop 1 and Warburg, Kubowitz and Christian 2 were the first to make any quantitative studies involving the interpretation of the action of methylene blue on hemoglobin. The latter state that methemoglobin does not accumulate during methylene blue catalysis when rabbit erythrocytes are placed in a saline-PO₄-glucose solution, but that it disappears as fast as formed, is reformed, disappears again and so on in a continuous cycle. The presence of glucose is necessary for demonstrating this catalytic effect of methylene blue because it is the reductant by which methemoglobin is transformed back to hemoglobin. Since leuco methylene blue is autoxidizable, this completes the cycle.

It could, therefore, be predicted that since a certain amount of glucose is present in the blood stream, methemoglobin would be reduced as fast as it was formed and that no appreciable amount of it would appear until there was no longer any glucose in the blood. This was proven by injecting more than a therapeutic dose into rats in the following experiments: rats (10 in each of 3 groups) were injected intraperitoneally with (1) NaNO₂; (2) methylene blue; (3) saline solution or nothing. The dose of NaNO₂ was 1 cc. of a 2% solution; of methylene blue, 1 cc. of a 0.1% solution, both per 100 gm. body weight. Both aqueous and saline solutions were used without any difference in results. The dose of methylene blue is 10 times that used in my former experiments 3 with CN and CO. NaNO₂ served as samples of blood with nearly complete transformation of hemoglobin to methemoglobin.