Nonspecific alkaline phosphatase activity can be responsible for staining of NADPH-diaphorase activity in certain non-neural cells.
The NADPH-diaphorase (NADPH-d) reaction is frequently used to visualize the diaphorase activity of nitric oxide synthase (NOS). However, this tetrazolium salt procedure can be of limited specificity at sites where non-specific alkaline phosphatase (alP) and NADHd activity co-exist. This is shown in the present paper using methods of catalytic histochemistry for these three enzymes and levamisole as alP inhibitor for certain mouse tissues. In the urothelium, portio, vaginal and endometrial epithelium as well as in some smooth muscle cells alP hydrolyzes NADPH to NADH which in turn serves as substrate for NADHd leading to false-positive formazan production. To exclude this possibility, it is recommended always to include levamisole in the incubation medium if the NADPHd activity of NOS has to be investigated.
Grozdanovic
Z
Z
Department of Anatomy, Free University of Berlin, Germany.
Gossrau
R
R
D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism; D004848:Epithelium / Q000201:enzymology; D005260:Female; D005562:Formazans / Q000378:metabolism; D006651:Histocytochemistry; D007527:Isoenzymes / Q000378:metabolism; D007978:Levamisole / Q000494:pharmacology*; D051379:Mice; D008815:Mice, Inbred Strains; D009130:Muscle, Smooth / Q000166:cytology / Q000201:enzymology; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D009580:Nitroblue Tetrazolium / Q000378:metabolism*; D013379:Substrate Specificity
D005562:Formazans; D007527:Isoenzymes; D007978:Levamisole; D009580:Nitroblue Tetrazolium; D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase; D008058:Dihydrolipoamide Dehydrogenase; D000469:Alkaline Phosphatase