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Am J Physiol Gastrointest Liver Physiol (September 21, 2001). doi:10.1152/ajpgi.00256.2001
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Articles in PresS, published online ahead of print September 21, 2001
Am J Physiol Gastrointest Liver Physiol, 10.1152/ajpgi.00256.2001
Submitted on June 14, 2001
Accepted on September 9, 2001

Cloning, expression and localization of a rat hepatocyte inward rectifier potassium channel

Ceredwyn E Hill1*, Martha Briggs1, Junjun Liu1, and Leslie Magtanong1

1 Physiology, Queen's University, Kingston, ON, Canada

* To whom correspondence should be addressed. E-mail: hillc{at}post.queensu.ca.

Bile formation involves anion accumulation within the apical lumen of hepatocytes. Potassium flux through hepatocellular basolateral membrane channels may provide the counterion for apical anion efflux. Here we cloned a molecular candidate for maintaining charge balance during bile secretion. Two transcripts resembling the Kir4.2 sub-class of inwardly-rectifying potassium channels were found. The putative longer isoform (4.2a) has 30 additional N-terminal amino acids, identifying this as a new isoform. The short form shared 86-91% identity with the mouse, human and guinea-pig channels. Whole-cell currents of either rat isoform expressed in HEK293T cells demonstrated time independence and inward rectification. Antibodies against a C-terminal fragment recognized bands between 40 and 45 kDa, 90 kDa, and a high molecular weight band around 200 kDa in overexpressing HEK cells. Immunohistology of liver tissue shows hepatocellular plasma membrane localization. In hepatocyte couplets Kir4.2 was predominantly localized to the basolateral membrane. The results demonstrate the expression of a new Kir4.2 isoform in the rat hepatocyte, whose functional properties are compatible with a role in maintaining electrical integrity of bile-generating hepatocytes.




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