title: Subcellular distribution of dihydropyridine isothiocyanate binding in guinea-pig ileal smooth muscle.
abstract: The subcellular distribution of the 3H--2,6-dimethyl-3,5-dicarbomethoxy-4(2-isothiocyano) phenyl-1,4-dihydropyridine (DPSCN) binding to guinea-pig ileal smooth muscle was studied by subcellular fractionation. Initial experiments on subcellular fractionation of 3H-DPSCN-labelled tissues by differential centrifugation showed that there was an excellent correlation between the levels of the label present in a fraction and the plasma membrane marker phosphodiesterase I (r = 0.98) but not between the label and the putative endoplasmic reticulum marker NADPH: cytochrome-c-reductase (r = 0.56) or the inner mitochondrial marker cytochrome-c-oxidase (r = 0.36). Centrifugation of the microsomes on a continuous sucrose density gradient showed an excellent correlation of the migration of the label with phosphodiesterase I activity (r = 0.93) but not with the activities of NADPH: cytochrome-c-reductase (r = 0.66) or cytochrome-c-oxidase (r = 0.44). Treatment of microsomes with digitonin (1 mg/ml) followed by centrifugation on continuous sucrose density gradients increased the weighted mean densities of the phosphodiesterase activity (plasma membrane marker) and the labelling by similar magnitudes (0.04 to 0.06 g/ml). The weighted mean densities of NADPH: cytochrome-c-reductase and the cytochrome-c-oxidase were not altered significantly. It is concluded that in the guinea-pig ileal smooth muscle, DPSCN labels the plasma membrane specifically.
authors.forename: A K
authors.initials: AK
authors.lastname: Grover
authors.forename: C Y
authors.initials: CY
authors.lastname: Kwan
authors.forename: E E
authors.initials: EE
authors.lastname: Daniel
authors.forename: S
authors.initials: S
authors.lastname: Ahmad
authors.forename: T
authors.initials: T
authors.lastname: Ramlal
authors.forename: P
authors.initials: P
authors.lastname: Oakes
authors.forename: D J
authors.initials: DJ
authors.lastname: Triggle
mesh_terms: D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D004072:Digitonin; D004095:Dihydropyridines; D003576:Electron Transport Complex IV / Q000378:metabolism; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism; D066298:In Vitro Techniques; D017879:Isothiocyanates; D009130:Muscle, Smooth / Q000378:metabolism* / Q000648:ultrastructure; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000378:metabolism; D043264:Phosphodiesterase I; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism*
chemical_list: D004095:Dihydropyridines; D017879:Isothiocyanates; C045531:2,6-dimethyl-3,5-dicarbomethoxy-4-(2-isothiocyano)phenyl-1,4-dihydropyridine; D009251:NADPH-Ferrihemoprotein Reductase; D003576:Electron Transport Complex IV; D010727:Phosphoric Diester Hydrolases; D043264:Phosphodiesterase I; D009543:Nifedipine; D004072:Digitonin