title: Purification and chemical characterization of a potent inhibitor of the Na-K-Cl cotransport system in rat urine.
abstract: A potent inhibitor of the Na-K-Cl cotransport system was purified from urines of salt-loaded rats. Mass spectroscopy revealed a molecular mass of 242 Da. Nuclear magnetic resonance showed a spectrum identical to that of 3,4-dihydro-3-(4-hydroxyphenyl)-2H-1-benzopyran-7-ol (an "estrogen-like" isoflavonoid: equol). This compound inhibited cotransport fluxes at similar concentrations (IC50=16-24 microM) as furosemide (IC50 approximately 10 microM). Cotransport inhibitory activity of urines from rats drinking tap water was fully explained by urinary equol concentrations (approximately 27 microM, measured by high-performance liquid chromatography). Slat-loading increased urinary equol excretion, but not sufficiently high to fully explain the very important increase in cotransport inhibitory potency. We conclude that: (i) under basal conditions urinary equol can regulate Na-K-Cl cotransport activity in the kidney and (ii) salt-loading should evoke the appearance of other cotransport inhibitors.
authors.affiliation: Physiology and Pharmacology, School of Medicine, University of Zaragoza, Spain.
authors.forename: J O
authors.initials: JO
authors.lastname: Alda
authors.forename: J A
authors.initials: JA
authors.lastname: Mayoral
authors.forename: M
authors.initials: M
authors.lastname: Lou
authors.forename: I
authors.initials: I
authors.lastname: Gimenez
authors.forename: R M
authors.initials: RM
authors.lastname: Martinez
authors.forename: R P
authors.initials: RP
authors.lastname: Garay
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000037:antagonists & inhibitors*; D002712:Chlorides / Q000378:metabolism; D002839:Chromans / Q000737:chemistry / Q000302:isolation & purification* / Q000652:urine; D060754:Equol; D007529:Isoflavones; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters
chemical_list: C007610:4',7-dihydroxy-3,4-dihydroisoflavone; D002352:Carrier Proteins; D002712:Chlorides; D002839:Chromans; D007529:Isoflavones; D028021:Sodium-Potassium-Chloride Symporters; D060754:Equol; D012964:Sodium; D011188:Potassium