| Project/Area Number |
04670520
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Circulatory organs internal medicine
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| Research Institution | University of Tokyo |
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Principal Investigator |
TAKAICHI Kenmei Univ. of Tokyo, Branchhospital, assistant Professor, 医学部(分), 助手 (00175423)
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| Co-Investigator(Kenkyū-buntansha) |
HANAI Junichi Univ. of Tokyo, Hospital, assistant professor, 医学部(病), 助手
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| Project Period (FY) |
1992 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1994: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1993: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1992: ¥700,000 (Direct Cost: ¥700,000)
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| Keywords | Na / H exchanger / NHE / NHE-1 / NHE-3 / Amiloride / Epithelium / Isoform / Targeting / アイソクォ-ム |
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| Research Abstract |
Several isoforms exist in Na/H exchangers (NHE) . It is generally believed that NHE-3, which is resistant to amiloride inhibition, is located in the apical membrane and NHE-1, which is sensitive to amiloride inhibition, is located in the basolateral membrane in the epithelial cells. We characterized NHE activity and its modulation in the cultured renal epithelial cells (OK cells and LLC-PK1 cells) .
We identified NHE activity in the basolateral membrane in addition to well known NHE activity in the apical membrane in OK cells. Since NHE in the both membranes is resistant to amiloride and its maximum activity is inhibited by parathyroid hormone, NHE in the both membranes seems to be NHE-3. Thus, NHE-3 can be expressed not only in the apical membrane but also in the basolateral membrane in OK cells. The affinity for cytosolic [H^+] of NHE in the basolateral membrane is different from that in the apical membrane. Thus, the character of NHE-3 may vary depending on the side where NHE-3 is located. Since OK cells transfected with human NHE-1 cDNA expressed NHE-1 activity only in the basolateral membrane, NHE-1 may have intrinsic signal to target itself to the basolateral membrane in the epithelial cells.
NHE activity in the apical membrane of LLC-PK1 cells is more sensitive to amiloride than typical NHE-3. To clarify whether NHE-1 activity might be expressed in the apical membrane as well as in the basolateral membrane, we examined the effects of NHE-1 antisense oligonucleotide. Since transfection with antisense oligonucleotide inhibited only basolateral NHE activity in LLC-PK1 cells, NHE in the only basolateral membrane is encoded by NHE-1 mRNA.
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