AJP - Cell Physiology, Vol 262, Issue 4 C845-C853, Copyright © 1992 by American Physiological Society
Regulation of Na(+)-K(+)-ATPase expression in cultured renal cells by incubation in hypertonic medium
J. W. Bowen
Department of Pharmacology, University of Missouri-Columbia School of Medicine 65212.
To determine whether alterations in cell volume affect
Na(+)-K(+)-adenosinetriphosphatase (ATPase) expression, a subclone of the
Madin-Darby canine kidney (MDCK) cell line was incubated in anisotonic
serum-free medium and alpha- and beta-subunit mRNA, Na(+)-K(+)-ATPase
activity, and active K+ transport were measured. In medium adjusted to 500
mosmol/kgH2O by adding NaCl, the alpha-subunit mRNA concentration was 2.93
+/- 0.14 (SE) times control and beta-mRNA was 1.93 +/- 0.27 times control.
When sucrose was added to increase osmolality, alpha-subunit mRNA increased
to 1.85 +/- 0.18 times control. Na(+)-K(+)-ATPase activity of homogenates
from cells incubated in 500 mosmol/kgH2O medium for 24 h increased to 2.62
+/- 0.52 times control when NaCl was added and 2.31 +/- 0.34 times control
when sucrose was added. Active K+ transport increased between 60 and 90%
after cells were incubated in 450 mosmol/kgH2O medium with either NaCl or
sucrose added. Stimulation of Na(+)-K(+)-ATPase expression in renal cells
facing hypertonic stress may represent a long-term mechanism that allows
cells to maintain cation gradients in a hypertonic environment.
