[Spectral studies of drug interactions with hemoglobin and cytochrome c (author's transl)]

We studied the drug-induced spectra of hemoglobin and cytochrome c using aniline, aminopyrine, hydrocortisone and prednisolone. The difference spectrum of methemoglobin induced by aniline or aminopyrine was similar to type II, and that of oxidized cytochrome c induced by aniline was similar to type I. Characteristic spectral change occurred with addition of hydrocortisone or prednisolone to each of methemoglobin, oxyhemoglobin and carboxyhemoglobin, and by addition of each drug to deoxyhemoglobin, respectively. Other spectral changes were attributed to oxidation-reduction reactions between the drugs and the hemoproteins. Each of the reduced forms of hemoglobin showed a higher affinity to aniline and aminopyrine than did methemoglobin. Each of the reduced forms of hemoglobin or reduced cytochrome c showed a higher affinity to aminopyrine than to aniline. It is interesting that not only cytochrome P-450, a hydrophobic hemoprotein, but also hemoglobin and cytochrome c, hydrophilic hemoproteins, showed the drug-induced difference spectra. These results suggest direct interactions between drugs and hemoproteins. Oxyhemoglobin had a lower affinity to drugs in hemolysate than in the buffer only.