Purification and chemical characterization of a potent inhibitor of the Na-K-Cl cotransport system in rat urine.
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.
Alda
J O
JO
Physiology and Pharmacology, School of Medicine, University of Zaragoza, Spain.
Mayoral
J A
JA
Lou
M
M
Gimenez
I
I
Martinez
R M
RM
Garay
R P
RP
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
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