AJP - Cell Physiology, Vol 243, Issue 3 124-C132, Copyright © 1982 by American Physiological Society
Increase in K+ and alpha-AIB active transport in CHO cells after low [K+] treatment
J. S. Graves and D. D. Wheeler
We have studied the effects of prolonged incubation in low [K+] medium
(approximately 0.3 mM) on both K+ and amino acid transport in Chinese
hamster ovary (CHO) cells. When incubated in low [K+] medium, CHO cells
redressed partially the loss of intracellular K+ after 12 h. After 24 h of
incubation, both the activity of Na+-K+-ATPase in crude homogenates, and
the transport capacity (Vmax) for ouabain-sensitive (i.e., active) K+
influx approximately doubled. The magnitude of the ouabain-insensitive
(i.e., passive) K+ influx decreased by 50%. Thus the regulatory response
involves an apparent increase in Na+-K+ pump and a decrease in K+ leak. The
transport capacity for the nonmetabolized amino acid, alpha-aminoisobutyric
acid (alpha-AIB), also increased after 24 h in low [K+] medium. The Vmax
for the Na+-dependent (i.e., active) alpha-AIB influx increased by about
150%, and the magnitude of the Na+-independent influx increased by 20-40%.
These changes in alpha-AIB transport result in a twofold greater capacity
to accumulate this amino acid. Thus the regulation of K+ and alpha-AIB
transport systems appears to be linked and possible mechanisms of this
linkage are discussed.
