Alpha-NADPH appears to be primarily oxidized by the NADPH-diaphorase activity of nitric oxide synthase (NOS).
Biochemical studies have shown that the NADPH-diaphorase (NADPH-d) activity of nitric oxide synthase (NOS) represents only a part of the total cellular diaphorase pool. Histochemically, NADPH-d activity can be demonstrated in cells expressing no constitutive NOS. Therefore, attempts aimed to improve the specificity of the NADPH-d reaction are currently being undertaken. In this study, the effect of replacing the natural and common diaphorase substrate beta-NADPH with the artificial stereoisomer alpha-NADPH on the extent of NADPH-d staining was examined. When beta-NADPH served as the substrate, discrete populations of central and peripheral neurons as well as numerous non-neural cells in many organs of common laboratory rodents (mouse, rat, gerbil, hamster, guinea pig) and marmosets were found to generate formazan. Substitution of alpha-NADPH for beta-NADPH resulted in reduced staining intensity of nerve cells and muscle fibers. Furthermore, alpha-NADPH-d staining of macula densa cells, enterocytes and granulocytes varied according to the species examined. No reaction was observed in most other cells which stained positively for beta-NADPH-d activity. Examination of adjacent sections, incubated for the demonstration of NOS-immunoreactivity, revealed that alpha-NADPH-d activity and NOS immunostaining are strictly colocalized in neurons, striated muscle fibers and, species-dependently, in macula densa cells. It can thus be concluded that, with the exception of gut granulocytes, alpha-NADPH is primarily metabolized by the reductase activity of NOS.
Grozdanovic
Z
Z
Department of Anatomy, Free University of Berlin, Germany.
Gossrau
R
R
D000818:Animals; D002144:Callithrix; D006224:Cricetinae; D005260:Female; D005849:Gerbillinae; D006651:Histocytochemistry; D008297:Male; D051379:Mice; D009249:NADP / Q000378:metabolism*; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000276:immunology / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar; D013045:Species Specificity
D009249:NADP; D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase