title: Nitric oxide synthase in rat brain is predominantly located at neuronal endoplasmic reticulum: an electron microscopic demonstration of NADPH-diaphorase activity.
abstract: Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) of the rat brain, apparently identical with nitric oxide (NO) synthase, was demonstrated at the electron microscopic level by means of the tetrazolium salt 2-(2'-benzothiazolyl)-5-styryl-3-(4'-phthalhydrazidyl)tetrazolium chloride (BSPT). BSPT is a non-osmiophilic compound that yields an insoluble, osmiophilic, and lipophobic formazan on reduction. The reaction product was deposited sharply on membranes of the endoplasmic reticulum including the nuclear envelope. Other membrane structures were, as a rule, free of reaction product, likewise mitochondria. Occasionally, however, the outer membrane of mitochondria was labeled, and their contents displayed a homogeneous, medium electron density. The findings suggest that NADPH-d, i.e. neuronal NO synthase, is a predominantly membrane-bound enzyme, which is ubiquitously distributed in cells of brain tissue, but highly concentrated in nerve cells described as 'NADPH-d-positive' at the light microscopic level.
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000648:ultrastructure; D006651:Histocytochemistry; D008854:Microscopy, Electron; D008928:Mitochondria / Q000201:enzymology; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D009474:Neurons / Q000201:enzymology* / Q000648:ultrastructure; D019001:Nitric Oxide Synthase; D051381:Rats; D017208:Rats, Wistar; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D009252:NADPH Dehydrogenase