The use of phenazinemethosulphate as an electron carrier in the histochemical demonstration of dehydrogenases

Summary The use of phenazine methosulfate (PMS) has been investigated in the histochemical demonstration of dehydrogenase in some organs of the rat. The demonstration of nicotinamid-adenine-dinucleotide (NAD) linked dehydrogenases, which in the conventional methods without PMS is dependent upon the localisation of reduced NAD (NADH)-diaphorase, is greatly hindered by PMS. This inhibition is caused by the inactivation of the diaphorase by PMS. However in tissues or cells lacking the diaphorase, the nucleotide-linked dehydrogenases can be made visible by the addition of PMS to the conventional dehydrogenase reagents. PMS strongly activates the nucleotide-independent dehydrogenases such as succinate dehydrogenase.