A voltage-gated K(+) current in renal inner medullary collecting duct cells.
We studied the K(+)-selective conductances in primary cultures of rat renal inner medullary collecting duct (IMCD) using perforated-patch and conventional whole cell techniques. Depolarizations above -20 mV induced a time-dependent outward K(+) current (I(vto)) similar to a delayed rectifier. I(vto) showed a half-maximal activation around 5.6 mV with a slope factor of 6.8 mV. Its K(+)/Na(+) selectivity ratio was 11.7. It was inhibited by tetraethylammonium, quinidine, 4-aminopyridine, and Ba(2+) and was not Ca(2+) dependent. The delayed rectifying characteristics of I(vto) prompted us to screen the expression of Kv1 and Kv3 families by RT-PCR. Analysis of RNA isolated from cell cultures revealed the presence of three Kv alpha-subunits (Kv1.1, Kv1.3, and Kv1.6). Western blot analysis with Kv alpha-subunit antibodies for Kv1.1 and Kv1.3 showed labeling of approximately 70-kDa proteins from inner medulla plasmatic and microsome membranes. Immunocytochemical analysis of cell culture and kidney inner medulla showed that Kv1.3 is colocalized with the Na(+)-K(+)-ATPase at the basolateral membrane, although it is also in the cytoplasm. This is the first evidence of recording, protein expression, and localization of a voltage-gated Kv1 in the kidney IMCD cells.
Escobar
Laura I
LI
Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, México City DF, 04510, México. jjboliv@servidor.unam.mx
Martínez-Téllez
Julio C
JC
Salas
Monica
M
Castilla
Salvador A
SA
Carrisoza
Rolando
R
Tapia
Dagoberto
D
Vázquez
Mario
M
Bargas
José
J
Bolívar
Juan J
JJ
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D025802:Electric Capacitance; D017097:Electric Impedance; D015640:Ion Channel Gating / Q000502:physiology; D007679:Kidney Medulla / Q000166:cytology; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000502:physiology*; D007700:Kinetics; D051664:Kv1.3 Potassium Channel; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism
C496975:Kcna3 protein, rat; D051664:Kv1.3 Potassium Channel; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D012964:Sodium; D011188:Potassium; D002118:Calcium