gms | German Medical Science

27. Wissenschaftlicher Kongress der Deutschen Hochdruckliga

Deutsche Liga zur Bekämpfung des hohen Blutdrucks – Deutsche Hypertonie Gesellschaft e. V.

26. bis 29.11.2003, Bonn

Parallel Downregulation of Chloride Channel CLC-K1 and Barttin mRNA by Furosemide in Thin Ascending Limb of Rat

Herabregulation von Chloridkanal CLC-K1 und Barttin mRNA durch Furosemid in der dünnen Henle-Schleife der Ratte

Meeting Abstract (Hypertonie 2003)

  • presenting/speaker T. Bergler
  • K. Wolf
  • M. Meier-Meitinger
  • A. Kurtz
  • B. Krämer

Hypertonie 2003. 27. Wissenschaftlicher Kongress der Deutschen Hochdruckliga. Bonn, 26.-29.11.2003. Düsseldorf, Köln: German Medical Science; 2004. Doc03hochV52

The electronic version of this article is the complete one and can be found online at:

Published: November 11, 2004

© 2004 Bergler et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.




In the past few years the pivotal role of CLC-K1 channels in maintaining salt and water homeostasis in the kidney has been established. In this study we aimed to investigate the influence of the loop diuretic furosemide on the gene expression of the kidney chloride channel CLC-K1 and its recently described functional subunit barrtin.


Male Sprague Dawley rats received the loop diuretic furosemide (12mg/kg/day) for six days. Rats had free access to 0.9% NaCl, 0.1% KCL solution to prevent volume depletion. Localisation and regulation of CLC-K1 and barrtin mRNA was analyzed by RNase protection assay and in situ hybridisation. Nephron specific regulations were investigated by microdissection and real time PCR quantification.


In furosemide treated rats CLC-K1 mRNA decreased to half in inner medulla. In renal cortex and outer medulla CLC-K1 mRNA levels were low and did not change. Under furosemide treatment barrtin mRNA was regulated in parallel with CLC-K1 mRNA. A significant mRNA decrease occured after furosemide treatment in inner medulla (0.5fold), whereas cortical and outer medulla levels remained unaffected. 35S in situ hybridisation confirmed the regulation and distribution seen in the RNase protection assay experiments. Microdissection of inner medullary collecting duct and thin limb of Henle`s loop followed by real time PCR revealed that CLC-K1 and barrtin mRNA regulation in inner medulla was limited to thin limb, whereas mRNA levels in collecting ducts were not affected by furosemide treatment.


Given that in inner medulla tissue CLC-K1 and barrtin are regulated in thin ascending limb of Henle`s loop, our findings would suggest that in states of furosemide treatment selective downregulation of CLC-K1 and barrtin mRNAs in thin limb plays a role in NaCl handling.