Mechanism of potassium transport across proximal tubule epithelium in the rat.
The mechanism of proximal tubule potassium reabsorption was studied by stopped-flow microperfusion and determination of potassium activities by ion-sensitive resin microelectrodes. The proximal tubule was unable to establish transepithelial potassium gradients. Perfusion with 20 mM K+ turned the lumen 3 mV more negative, an effect abolished by Ba2+. The half-time for K+ activities to reach their stationary level after perfusion with 1 mM K+ was significantly increased by Ba2+ from 4.25 +/- 0.14 s to 11.0 +/- 1.71 s, and after perfusion with 20 mM K+, from 5.43 +/- 0.20 to 12.53 +/- 0.90 s. These data indicate that a significant fraction of potassium is transferred across proximal tubule epithelium by a transcellular, K(+)-channel-dependent route.
Vestri
S
S
Departamento de Fisiologia e Biofísica, Universidade de São Paulo, Brasil.
Malnic
G
G
D000818:Animals; D001464:Barium / Q000494:pharmacology; D001692:Biological Transport; D004848:Epithelium / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D010477:Perfusion; D011188:Potassium / Q000493:pharmacokinetics*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains
D015221:Potassium Channels; D001464:Barium; D011188:Potassium