Evidence from 23Na NMR studies for the existence of sodium-channels in the brush border membrane of the renal proximal tubule.
A fast Na+-exchange is shown to be present in isolated renal brush border membranes. The lower limit of the rate constant for this process, calculated from the 23Na-NMR spectrum is 580 sec-1. The actual exchange rate may be higher. A fast 7Li exchange is also shown to be present in the isolated membrane vesicles. The characteristic overshoot of the Na+ dependent D-glucose cotransport and Na+/H+ antiport can be demonstrated. The fact that neither treatment with papain, nor lowering of the temperature to 5 degrees C affected the 23Na-NMR spectra obtained in the renal brush border membrane vesicles is consistent with the possibility that the fast Na+-exchange occurs through a channel mechanism.
Elgavish
G A
GA
Elgavish
A
A
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D007473:Ion Channels / Q000032:analysis*; D007687:Kidney Tubules, Proximal / Q000648:ultrastructure*; D009682:Magnetic Resonance Spectroscopy; D008871:Microvilli / Q000032:analysis; D009004:Monosaccharide Transport Proteins; D010206:Papain / Q000378:metabolism; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*; D012975:Sodium Isotopes; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D007473:Ion Channels; D009004:Monosaccharide Transport Proteins; D012975:Sodium Isotopes; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D012964:Sodium; D010206:Papain