Inhibition by Glucose of Methemoglobin Formation

The purpose of these experiments is to show that injection of glucose prevents the formation of methemoglobin in animals, or if methemoglobin is already present, it can by the same means be reduced to hemoglobin which is then readily oxygenated to oxyhemoglobin.

Methemoglobin was produced experimentally in rabbits by injections of 0.15 gm. of NaNO₂ for every kg. of body weight. This dose converted 15% of the blood-hemoglobin into methemoglobin in a few minutes. This is less than the theoretical effect predicted by Wendel 1 for this dose, owing no doubt to the constant presence of glucose normally in the blood stream. Glucose was used in amounts of 1 cc. to 2 cc. of a 1% solution for every kg. body weight. All solutions were made up fresh with 0.9% NaCl and injected intravenously into one ear of the rabbit; blood samples were taken from the other ear at intervals thereafter.

The spectrophotometry method was used for determining the proportions of methemoglobin in blood. This method is sensitive to less than 2%. The ratio, R, of the extinction coefficient at λ = 540 mμ to that at λ = 560 mμ, as found by Ray, Blair and Thomas 2 indicates the per cent of methemoglobin present. All blood samples were diluted to 1% with 0.4% NH₄OH. No difference in readings was noted when water was used as a diluent. The thickness of the layer measured was 1 cm. Five animals were used in each group. The probable error of the readings was a fraction of 1%. The method is also valuable because determinations can be made so quickly that chemical changes following collection are minimized.

Results in vivo. Methemoglobin was produced in the rabbit as indicated above, the R value found being 1.56 which indicates 15% conversion to methemoglobin.