title: The effects of urinary digitalislike factor on cultured vascular smooth muscle cells.
abstract: We attempted to purify a digitalislike factor from human urine. On the assumption that a natural ligand for the digitalis receptor should be searched for on the basis of the effects on intact cells, we used an inhibitory effect on the binding of [3H]ouabain to human erythrocytes to determine digitalislike activity. A highly polar [3H]ouabain displacing activity was obtained by a combination of chromatographic procedures including reverse-phase high performance liquid chromatography. Urine-derived [3H]ouabain displacing activity, a competitive inhibitor of ouabain binding to human erythrocytes, acted on human lymphocytes in a similar manner. The dose-response curve of this compound was parallel to that of ouabain. Urine-derived [3H]ouabain displacing activity significantly inhibited monensin-stimulated increase in ouabain-sensitive 86Rb uptake, a parameter of Na+,K+-adenosine triphosphatase (ATPase), by 95% (p less than 0.01) in cultured vascular smooth muscle cells (A10 cells). Furthermore, this compound enhanced net 45Ca influx by 30% (p less than 0.01) and reduced 45Ca efflux by 35% (p less than 0.01) in A10 cells. These results suggest that urine-derived [3H]ouabain displacing activity may be a regulator of Na+,K+-ATPase and a modulator of vascular tone.
authors.affiliation: Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Goto
authors.forename: K
authors.initials: K
authors.lastname: Yamada
authors.forename: M
authors.initials: M
authors.lastname: Ishii
authors.forename: M
authors.initials: M
authors.lastname: Yoshioka
authors.forename: T
authors.initials: T
authors.lastname: Ishiguro
authors.forename: T
authors.initials: T
authors.lastname: Sugimoto
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002298:Cardenolides; D002478:Cells, Cultured; D004077:Digoxin; D004910:Erythrocyte Membrane / Q000378:metabolism; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D010042:Ouabain / Q000378:metabolism; D051381:Rats; D012413:Rubidium / Q000378:metabolism; D012503:Saponins; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism; D014556:Urine / Q000032:analysis*
chemical_list: D001798:Blood Proteins; D002298:Cardenolides; D012503:Saponins; C034504:digoxin-like factors; D010042:Ouabain; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D002118:Calcium