AJP - Gastrointestinal and Liver Physiology, Vol 256, Issue 5 868-G877, Copyright © 1989 by American Physiological Society
Putrescine uptake and release by colon cancer cells
S. A. McCormack and L. R. Johnson
Department of Physiology and Cell Biology, University of Texas Medical School, Houston 77225.
We have investigated the uptake and release of [3H]putrescine by a human
colon adenocarcinoma cell line (LoVo) maintained on filter inserts. This
culture system permits the cells to develop morphological polarity and
provides separate access to the basolateral and apical surfaces of the
cells. [3H]putrescine was taken up more readily by the basolateral than by
the apical side of the cells. [3H]putrescine uptake could be stimulated
greater than 300 times by either 10 mM asparagine or 10% fetal bovine
serum. [3H]putrescine was accumulated to a concentration gradient of
approximately 300-fold; uptake could be inhibited 50% by 7.5 microM
unlabeled putrescine and was not dependent on Na+. The release of
[3H]putrescine into the apical medium was inhibited by asparagine or fetal
bovine serum. Usually, less than one-thousandth of the [3H]putrescine taken
up into the cells was released into the apical medium. Release of
[3H]putrescine did not correspond to the accumulation of [14C]-inulin in
the apical medium. For these reasons we concluded that putrescine release
was not simply passive leakage but was responsive to intracellular demand.
The [3H]putrescine taken up by the cells as well as that released into the
apical medium was greater than 90% unmetabolized at 4h.
