Upregulation of apical NHE3 in renal OK cells overexpressing the rodent alpha(1)-subunit of the Na+ pump

• Type: Article in International Scientific Journal
• Date: 2006

Authors

Pedro Gomes (Author) Other; soares-da-silva, p (Author) FMUP

Journal

Title: American Journal of Physiology - Regulatory Integrative and Comparative Physiology

Vol. 290

ISSN: 0363-6119

Publisher: American Physiological Society

Indexing

ISI Web of Knowledge - 11 Citations

Scopus - 11 Citations

Other information

Authenticus ID: P-004-MAT

DOI: 10.1152/ajpregu.00102.2005

Abstract (EN): Upregulation of apical NHE3 in renal OK cells overexpressing the rodent alpha(1)-subunit of the Na+ pump. Am J Physiol Regul Integr Comp Physiol 290: R1142-R1150, 2006. First published November 17, 2005; doi:10.1152/ajpregu.00102.2005. Vectorial Na+ reabsorption across the proximal tubule is mediated by apical entry of Na+, primarily via Na+/H+ exchanger isoform 3 (NHE3), and basolateral extrusion via the Na+ pump (Na+-K(+)ATPase). We hypothesized that regulation of Na+ reabsorption should involve not only the activity of the basolateral Na+-K(+)ATPase, but also the apical NHE3, in a concerted manner. To generate a cell line that overexpresses Na+-K+-ATPase, opossum kidney (OK) cells were transfected with the rodent Na+-K+-ATPase alpha(1)-subunit (pCMV ouabain vector), and native cells were used as a control. The existence of distinct functional classes of Na+-K+-ATPase in wildtype and transfected cells was confirmed by the inhibition profile of Na+-K+-ATPase activity by ouabain. In contrast to wild-type cells, transfected cells exhibited two IC50 values for ouabain: the first value was similar to the IC50 of control cells, and the second value was 2 log units greater than the first, consistent with the presence of rat and opossum alpha(1)-isozymes. It is shown that transfection of OK cells with Na+-K+-ATPase increased Na+-K+-ATPase and NHE3 activities. This was associated with overexpression of the Na+-K+-ATPase alpha(1)-subunit and NHE3 in transfected OK cells. The abundance of the Na+-K+-ATPase alpha(1)-subunit was slightly lower in transfected OK cells. In conclusion, the increase in expression and function of Na+-K+-ATPase in cells transfected with the rodent Na+ pump alpha(1)-subunit cDNA is expected to stimulate apical Na+ influx into the cells, thereby accounting for the observed stimulation of the apical NHE3 activity.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9