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This Article Full Text Full Text (PDF) All Versions of this Article: 287/3/L510    most recent 00021.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Iwamoto, L. M. Articles by Wada, R. K. Search for Related Content PubMed PubMed Citation Articles by Iwamoto, L. M. Articles by Wada, R. K.

Na-K-2Cl cotransporter inhibition impairs human lung cellular proliferation

¹Department of Pediatrics, Kapiolani Medical Center for Women and Children and John A. Burns School of Medicine; ²Clinical Research Center, and ³Cancer Etiology Program, Cancer Research Center, University of Hawaii, Honolulu, Hawaii 96822

Submitted 22 January 2004 ; accepted in final form 4 May 2004

The widespread presence of the Na-K-2Cl (NKCC) cotransporter protein suggests that chronic administration of inhibitors may result in adverse effects. Inhibition of the NKCC cotransporter by loop diuretics is felt to underlie the diuretic and the pulmonary smooth muscle relaxant effects of this drug class. However, the fundamental regulation of salt and water movement by this cotransporter suggests that it may also mediate cell volume changes occurring during cell cycle progression. Thus we hypothesized that NKCC cotransporter inhibition by loop diuretics would decrease cellular proliferation. Normal human bronchial smooth muscle cells (BSMC) showed a significant concentration-dependent decrease in cell counts after 7 days of exposure to both bumetanide (n = 5–10) and furosemide (n = 6–16) compared with controls. Proliferation was similarly inhibited in normal human lung fibroblasts (n = 5–9). To determine whether this was due to loss of cells, we performed apoptosis assays on BSMC. Both annexin V-propidium iodide staining (n = 5–10) and single cell gel electrophoresis assays (n = 4) were negative for necrosis and apoptosis in BSMC exposed to 10 µM bumetanide. Subsequent analysis of the cell cycle by flow cytometry showed that bumetanide-exposed BSMC were delayed in G₁ phase compared with controls (n = 4–8). This is the first evidence for loop diuretic inhibition of airway smooth muscle cell proliferation. NKCC cotransporter inhibition impeded G₁-S phase transition without facilitating cell death. Thus although inhibition by loop diuretics relaxes airway smooth muscle, the NKCC cotransporter may have a more important role in cell proliferation regulation.

furosemide; bumetanide

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