Abstract
The extraordinary cyanosis shown by patients during sulphanilamide therapy has received no explanation.
Marshall, 1 King, 2 and others have demonstrated that the respiratory function of the hemoglobin is unaltered. Methemoglobin and sulphemoglobin have been found in some cases but in amounts far too small to explain the intense cyanosis. The plasma of cyanotic patients appears normal. Whole blood, whether arterial or venous, has a chocolate brownish tinge. Though such blood when aerated gains oxygen in normal amounts it does not become bright red but remains dark. This led us to seek for a colored derivative of sulphanilamide in the erythrocytes.
After various unsuccessful attempts we were led by the known helio-sensitivity of sulphanilamide-treated patients to try the effect of ultraviolet light. This enabled us to reproduce the phenomenon in vitro and to offer an explanation for the cyanosis.
We found that dilute solutions of sulphanilamide on very brief exposure to ultraviolet light develop a strong violet color. The nature of the chemical change is so far unknown.
When red cells are added to such solutions they at once adsorb the violet substance from the supernatant fluid and assume the color shown by the red cells of patients under sulphanilamide therapy. Plasma added to the violet solutions causes the color to disappear.
The violet substance is only the first of several colors produced by irradiation of sulphanilamide. It is developed only by irradiation of short duration, one half to one or at most 3 minutes. When irradiation is continued for longer periods the color rapidly changes to yellow, then brownish.
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