On the oxygen-sensitivity of various tetrazolium salts

Summary 1. Eight different tetrazolium salts have been chemically reduced with NADPH and PMS¹ under oxygenated and oxygen-free conditions. 2. PMS has been shown to be able to remove all of the hydrogen from NADPH very rapidly, and to transfer all of this hydrogen onto tetrazolium salts, under suitable atmospheric conditions. 3. MTT, INT, TNBT, and NBT¹ produced the same amount of formazan under both conditions; NT BT, TV, TT¹ produced formazan under oxygen-free conditions, but produced no formazan under oxygenated conditions. 4. These results are explained on the basis of competition for the NADP Hhydrogen between oxygen and the four tetrazolium salts NT, BT, TV and TT.I should like to thank The Arthritis and Rheumatism Council for financial support.