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Diverse expression of Kir contributes to different resting membrane potential distribution among the cochlear, brain and mesenteric arterioles
Author(s) -
Yang YuQin,
Ma KeTao,
Karasawa Takatoshi,
Shi XiaoRui,
Nuttall Alfred L,
Jiang ZhiGen
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1145.9
Subject(s) - sma* , depolarization , membrane potential , chemistry , constriction , superior mesenteric artery , biophysics , anatomy , population , biology , medicine , endocrinology , mathematics , environmental health , combinatorics
The resting membrane potentials (RP) of the spiral modiolar artery (SMA) cells exhibit a prominent bimodal distribution peaked near −75 and −40 mV. The RPs of brain artery (BA) also showed a bimodal pattern but with a dominating population around −77 mV, while the mesenteric arterial (MA) displayed a skewed single peak distribution around −72 mV. Using intracellular and whole‐cell recording, immunocytochemical and molecular biological detection of Kir2.x expression, we tested a hypothesis that a diverse expression of Kir underlies the distinct RP distribution. We found that: 1) bathing of 10 mM K + caused a −7.1, 6.7 and 9.8 mV membrane potential change, 2) 20 mM K + usually caused a dilation, biphasic dilation followed by a constriction, and only a constriction in the SMA, BA and MA, respectively. 3) Ba 2+ caused a depolarization in high RP cells with an EC 50 of 89, 158 and 201 μM for the SMA, BA and MA, respectively. 4) A robust K ir current in 60 mM K + was recorded more frequently in BA and MA than the SMA. Ba 2+ suppressed the K ir current with an IC 50 of 561 ± 73, 446 ± 30 and 811 ± 49 nM at −120 mV for the SMA, BA and MA. 5) Kir2.1 immunoreactive signal was detected in smooth muscle not endothelial cells of all the vessels. Western blotting data revealed that the SMA, BA and MA express Kir2.1 protein at a ratio of 1.0:1.1:0.83. 6) RT‐PCR analysis showed that the four Kir2.x isoforms all had mRNA transcripts in the three vessels but Kir2.3 was higher in BA and MA than SMA, while Kir2.4 was higher in the SMA than BA and MA. We conclude that heterogeneous expression of Kir2.x subunits may form different heteromeric channels and channel densities in the three vessels, thus contributing to the distinct RP distributions. Supported by NIH DC 004716 (ZGJ) & DC 00105 (ALN).