title: Estimated potassium reflection coefficient in perfused proximal convoluted tubules of the anaesthetized rat in vivo.
abstract: 1. As yet there is no definitive description of the mechanism and route by which K+ reabsorption is achieved in the proximal convoluted tubule (PCT). We have assessed the contribution of convective K+ transport to net potassium ion flux (JK) by estimating the reflection coefficient of K+ (sigma K) in the proximal tubule of anaesthetized rats previously prepared for in vivo microperfusion. 2. Alterations in the luminal concentration of the impermeant solute raffinose in single-perfused (lumen only) and double-perfused (lumen and capillaries) PCTs were found to change fluid reabsorption in a predictable fashion. 3. Net potassium ion flux (JK) in single- and double-perfused tubules was significantly correlated with net fluid flux (Jv), suggesting that convective K+ transport may be a significant factor in overall K+ transport by the PCT. 4. Estimates of sigma K in single- and double-perfused tubules were very similar (0.14 +/- 0.06 and 0.13 +/- 0.05, respectively), even though K+ diffusion was not strictly controlled in the former group. The maximum effect of 'pseudo-solvent' drag in double-perfused tubules was estimated to give a sigma K of 0.40. This low value for sigma K suggests that true convection/solvent drag may be an important driving force for the reabsorption of K+ from the PCT of the rat.
authors.affiliation: School of Biological Sciences, University of Manchester, UK.
authors.forename: M
authors.initials: M
authors.lastname: Wareing
authors.forename: R W
authors.initials: RW
authors.lastname: Wilson
authors.forename: J D
authors.initials: JD
authors.lastname: Kibble
authors.forename: R
authors.initials: R
authors.lastname: Green
mesh_terms: D000758:Anesthesia; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D004848:Epithelium / Q000378:metabolism / Q000648:ultrastructure; D007444:Inulin; D007473:Ion Channels / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D011188:Potassium / Q000378:metabolism*; D011887:Raffinose / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D014316:Tritium; D014867:Water / Q000378:metabolism
chemical_list: D007473:Ion Channels; D014867:Water; D014316:Tritium; D007444:Inulin; D012964:Sodium; D011887:Raffinose; D011188:Potassium