AJP - Cell Physiology, Vol 259, Issue 4 C647-C653, Copyright © 1990 by American Physiological Society
Nonmetabolizable glucose analogues and ornithine decarboxylase expression in LLC-PK1 cells
D. W. Lundgren and C. V. Vacca
Department of Pediatrics, Case Western Reserve Univesity, Cleveland, Ohio 44109.
This report examines the effect of nonmetabolizable glucose analogues on
ornithine decarboxylase (ODC) activity in LLC-PK1 cells. The addition of
Na(+)-dependent cotransported glucose analogues,
1-O-methyl-alpha-D-glucopyranoside (alpha-MDG) and
1-O-methyl-beta-D-glucopyranoside, to Earle's balanced salt solution minus
glucose (EBSS-G) increased ODC activity five- to sevenfold above basal
levels. The passive carrier-mediated transported glucose analogue
3-O-methyl-D-glucopyranose had very little effect on enzyme activity.
alpha-MDG increased ODC activity in quiescent but not growing cells. ODC
activity increased as a function of both the incubation time in EBSS-G +
alpha-MDG and the concentration of alpha-MDG in EBSS-G. Phlorizin
significantly reduced the level of enzyme activity induced by alpha-MDG.
ODC expression by alpha-MDG was reduced in cells incubated in hypertonic
EBSS-G + alpha-MDG. Enzyme activity, in the absence of extracellular
organic substrates, was markedly elevated in cells incubated in hypotonic
media. It is suggested that an influx of Na+ and/or an increase in cell
volume elevates one or more signal transducers that regulate ODC
expression.
