title: Voltage dependence and barium sensitivity of colonic K secretion in renal failure.
abstract: Net colonic K secretion (JKnet) is increased in rats and humans with chronic renal failure (CRF). To study whether transepithelial potential difference (PD), active transport forces and/or luminal K conductance play a role in this adaptation, experiments were performed in the colon of control, K-adapted, and CRF rats. Under basal conditions the PD in vivo in CRF was greater than in controls and not different from K-adapted rats. JKnet was comparable in vivo in CRF and K-adapted rats and was greater than in controls. Amiloride (10 microM) reduced PD and JKnet in K-adapted and CRF rats to levels comparable to controls. Under in vitro short-circuited conditions serosal-to-mucosal K flux (JKs----m) in distal colon was significantly increased in K-adapted and CRF animals compared with control, whereas barium caused a significant reduction in JKs----m in all groups of animals. The barium-sensitive component of K secretion was greater, however, in the two experimental groups (-0.2 +/- 0.02 and -0.2 +/- 0.07 in K-adapted and CRF animals, respectively, vs. -0.08 +/- 0.02 microeq.h-1.cm-2 in controls, P less than 0.05). However, luminal barium failed to completely inhibit the increase in K secretion observed in the experimental groups. These data suggest that an increase in PD that results in a rise in luminal negativity, stimulation of active transport, and an increase in barium-sensitive K channels and barium-insensitive pathways in apical membrane of distal colon participate in the mechanism by which net K secretion is increased in the large intestine of subjects with CRF.
authors.affiliation: Instituto de Investigaciones Médicas Alfredo Lanari, University of Buenos Aires, Argentina.
authors.forename: E L
authors.initials: EL
authors.lastname: Siga
authors.forename: R S
authors.initials: RS
authors.lastname: Martin
authors.forename: C
authors.initials: C
authors.lastname: Ibarra
authors.forename: D
authors.initials: D
authors.lastname: Verón
authors.forename: F
authors.initials: F
authors.lastname: Ibarra
authors.forename: M
authors.initials: M
authors.lastname: Giménez
authors.forename: M
authors.initials: M
authors.lastname: Parisi
authors.forename: E
authors.initials: E
authors.lastname: Arrizurieta
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology*; D001693:Biological Transport, Active; D003106:Colon / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D004195:Disease Models, Animal; D004553:Electric Conductivity; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D007676:Kidney Failure, Chronic / Q000503:physiopathology*; D008297:Male; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
chemical_list: D001464:Barium; D000584:Amiloride; D011188:Potassium