Expression and functional properties of unique inward rectifier K+ channel Kir7.1 in the porcine iris and retinal pigment epithelium.
OBJECTIVE
To investigate the membrane functional properties of porcine iris pigment epithelial cells (IPE), and compare the characters of inward rectifier potassium (Kir) channel in the IPE with those in the retinal pigment epithelial cells (RPE).


METHODS
IPE and RPE were acutely dissociated from porcine eyes. Functional properties of Kir channels were characterized using whole cell patch clamp recording techniques. Expression of Kir7.1 mRNA in both cells was detected by reverse transcription-polymerase chain reaction (RT-PCR).


RESULTS
Whole cell current in the IPE exhibited a mild inward K+ rectification, and showed little dependence on [K+]o. Unusual high (7.04 +/- 1.7) Rb+ to K+ inward conductance ratio indicated that Kir7.1 subunit was expressed in the IPE as the same as RPE cells. Also, Kir7.1 mRNA was detected in both porcine IPE and RPE by RT-PCR. However, functional expression of Kir conductance in IPE cells (21.7 S/F) was much smaller than that in RPE cells (205.6 S/F).


CONCLUSIONS
The Kir7.1 subunit was predominantly expressed in the acutely dissociated porcine IPE and its functional properties are similar to those in the RPE. However, the current density seems too small to fulfill the task of the Kir function of RPE.
Yasuda
Kanako
K
Department of Ophthalmology, Tohoku University, School of Medicine, Sendai Miyagi, Aoba, Japan.
Shimura
Masahiko
M
Nakazawa
Toru
T
Sato
Hajime
H
Tomita
Hiroshi
H
Sugano
Eriko
E
Tamai
Makoto
M
D000818:Animals; D004553:Electric Conductivity; D004594:Electrophysiology; D007498:Iris / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010539:Permeability; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics* / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013552:Swine
D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger