The ROMK potassium channel is present in mammalian urinary tract epithelia and muscle.
There is increasing evidence that mammalian urinary tract epithelial cells utilize membrane channels and transporters to transport solutes across their apical (luminal) and basalateral membranes to modify solute concentrations in both cell and urine. This study investigates the expression, localization, and regulation of the ROMK (K(ir) 1.1) potassium channels in rat and dog ureter and bladder tissues. Immunoblots of homogenates of whole ureter, whole bladder, bladder epithelial cells, and bladder smooth muscle tissues in both rat and dog identified approximately 45- to 50-kDa bands characteristic of ROMK in all tissues. RT-PCR identified ROMK mRNA in these same tissues in both animal species. ROMK protein localized by immunocytochemistry was strongly expressed in the apical membranes of the large umbrella cells lining the bladder lumen and to a lesser extent in the cytoplasm of epithelial cells and smooth muscle cells in the rat bladder. ROMK protein and mRNA were also discovered in cardiac, striated, and smooth muscle in diverse organs. There was no difference in immunoblot expression of ROMK abundance in bladder homogenates (whole bladder, epithelial cell, or muscle cell) or ureteral homogenates between groups of rats fed high- or low-potassium diets. Although the functional role of ROMK in urinary tract epithelia and smooth muscle is unknown, ROMK may participate in the regulation of epithelial and smooth muscle cell volume and osmolality, in the dissipation of potassium leaked or diffused from urine across the epithelial cell apical membranes or tight junctions, and in net or bidirectional potassium transport across urinary tract epithelia.
Spector
David A
DA
Johns Hopkins Bayview Medical Center, Division of Renal Medicine, B2N, 4940 Eastern Ave., Baltimore, MD 21224, USA. dspector@jhmi.edu
Yang
Qing
Q
Klopouh
Leonid
L
Deng
Jie
J
Weinman
Edward J
EJ
Steplock
Deborah A
DA
Biswas
Rajatsubhra
R
Brazie
Marc F
MF
Liu
Jie
J
Wade
James B
JB
D000818:Animals; D004847:Epithelial Cells / Q000502:physiology; D005260:Female; D041981:Gastrointestinal Tract / Q000502:physiology; D006321:Heart / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology*; D011188:Potassium / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014513:Ureter / Q000502:physiology; D001743:Urinary Bladder / Q000502:physiology; D014551:Urinary Tract / Q000378:metabolism
C510692:Kcnj1 protein, rat; D024661:Potassium Channels, Inwardly Rectifying; D011188:Potassium
Kidney Int. 1998 Oct;54(4):1214-23
9767537
Kidney Int. 2007 Sep;72(5):566-73
17579662
Am J Physiol Renal Physiol. 2004 Jul;287(1):F102-8
15068976
J Biol Chem. 2002 Oct 4;277(40):37871-80
12122007
J Physiol. 1997 Dec 1;505 ( Pt 2):503-11
9423189
Biol Rev Camb Philos Soc. 1975 May;50(2):215-46
1100129
Eur Urol. 1987;13(1-2):83-9
3582458
Biochemistry. 2003 Nov 4;42(43):12662-8
14580213
Am J Physiol Renal Physiol. 2005 Nov;289(5):F1065-71
16210451
Am J Physiol Renal Physiol. 2003 Dec;285(6):F1179-87
12952855
Am J Physiol Renal Physiol. 2003 Oct;285(4):F651-63
12770841
J Urol. 1990 Jan;143(1):139-42
1688456
J Urol. 1987 Aug;138(2):433-7
3599272
Am J Physiol Renal Physiol. 2004 May;286(5):F881-92
15075184
J Urol. 1995 Jul;154(1):6-15
7776457
Am J Physiol Renal Physiol. 2002 Jun;282(6):F1034-42
11997319
Urol Int. 1985;40(4):211-6
3901473
Am J Physiol. 1959 Mar;196(3):549-53
13627221
Am J Physiol. 1994 Nov;267(5 Pt 1):C1483-92
7977709
Am J Physiol Renal Physiol. 2007 Jan;292(1):F467-74
16849692
J Gen Physiol. 1986 Apr;87(4):567-90
3701299
Am J Physiol Cell Physiol. 2007 Jan;292(1):C106-14
16837648
J Physiol. 1998 Jun 15;509 ( Pt 3):629-34
9596787
Am J Physiol Renal Physiol. 2002 Dec;283(6):F1200-7
12388410
J Membr Biol. 1991 May;122(1):77-88
1652031
FEBS Lett. 1996 Dec 9;399(1-2):122-6
8980134
Am J Physiol. 1960 Jan;198:191-4
14436265
J Am Soc Nephrol. 2001 Jan;12(1):10-18
11134245
Am J Physiol. 1997 Nov;273(5):F739-48
9374837
J Am Soc Nephrol. 1997 Dec;8(12):1823-30
9402083
Am J Physiol. 1956 Feb;184(2):406-11
13302434
Mayo Clin Proc. 1975 Mar;50(3):141-6
1117761
Am J Physiol. 1988 Aug;255(2 Pt 2):F244-9
3407782
Invest Urol. 1964 Sep;2:145-53
14206405
Am J Physiol Renal Physiol. 2000 Jun;278(6):F867-74
10836974
Am J Physiol. 1998 Jan;274(1):F91-6
9458827
Am J Physiol. 1996 Oct;271(4 Pt 2):F886-94
8898019
J Membr Biol. 1976 Aug 27;28(1):1-40
9512
Am J Physiol Renal Physiol. 2000 Jun;278(6):F916-24
10836979