title: Potassium secretion by voltage-gated potassium channel Kv1.3 in the rat kidney.
abstract: The fine regulation of Na(+) and K(+) transport takes place in the cortical distal nephron. It is well established that K(+) secretion occurs through apical K(+) channels: the ROMK and the Ca(2+)- and voltage-dependent maxi-K. Previously, we identified the voltage-gated Kv1.3 channel in the inner medulla of the rat kidney (Escobar LI, Martínez-Téllez JC, Salas M, Castilla SA, Carrisoza R, Tapia D, Vázquez M, Bargas J, Bolívar JJ. Am J Physiol Cell Physiol 286: C965-C974, 2004). To examine the role of Kv1.3 in the renal regulation of K(+) homeostasis, we characterized the effect of dietary K(+) on the molecular and functional expression of this channel. We performed real-time-PCR and immunoblot assays in kidneys from rats fed a control (CK; 1.2% wt/wt) or high-K(+) (HK; 10% wt/wt) diet for 5-15 days. Kv1.3 mRNA and protein expression did not change with HK in the whole kidney. However, dietary K(+) loading provoked a change in the cellular distribution of Kv1.3 from the cytoplasm to apical membranes. Immunolocalization of Kv1.3 detected the channel exclusively in the intercalated cells. We investigated whether Kv1.3 mediated K(+) transport in microperfused cortical collecting ducts (CCDs). The HK diet led to an increase in net K(+) transport from 7.4 +/- 1.1 (CK) to 11.4 +/- 1.0 (HK) pmol x min(-1.) mm(-1). Luminal margatoxin, a specific blocker of Kv1.3, decreased net K(+) secretion in HK CCDs to 6.0 +/- 1.6 pmol x min(-1.) mm(-1). Our data provide the first evidence that Kv1.3 channels participate in K(+) secretion and that apical membrane localization of Kv1.3 is enhanced in the intercalated cells by dietary K(+) loading.
authors.affiliation: Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, México.
authors.forename: Rolando
authors.initials: R
authors.lastname: Carrisoza-Gaytán
authors.forename: Carolina
authors.initials: C
authors.lastname: Salvador
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Satlin
authors.forename: Wen
authors.initials: W
authors.lastname: Liu
authors.forename: Beth
authors.initials: B
authors.lastname: Zavilowitz
authors.forename: Norma A
authors.initials: NA
authors.lastname: Bobadilla
authors.forename: Joyce
authors.initials: J
authors.lastname: Trujillo
authors.forename: Laura I
authors.initials: LI
authors.lastname: Escobar
mesh_terms: D000818:Animals; D015153:Blotting, Western; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D015640:Ion Channel Gating; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D051664:Kv1.3 Potassium Channel / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D008856:Microscopy, Fluorescence; D010477:Perfusion; D026902:Potassium Channel Blockers / Q000494:pharmacology; D017419:Potassium, Dietary / Q000378:metabolism* / Q000652:urine; D021381:Protein Transport; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012604:Scorpion Venoms / Q000494:pharmacology; D013997:Time Factors; D016482:Urinalysis
chemical_list: C496975:Kcna3 protein, rat; D051664:Kv1.3 Potassium Channel; D026902:Potassium Channel Blockers; D017419:Potassium, Dietary; D012333:RNA, Messenger; D012604:Scorpion Venoms; C077910:margatoxin