AJP - Renal Physiology, Vol 259, Issue 4 653-F659, Copyright © 1990 by American Physiological Society
Modulation of osmolytes in MDCK cells by solutes, inhibitors, and vasopressin
C. W. Heilig, R. M. Brenner, A. S. Yu, B. C. Kone and S. R. Gullans
Renal Division, Brigham and Women's Hospital, Boston, Massachusetts.
MDCK cells accumulate organic osmolytes in response to hyperosmotic
NaCl-supplemented medium. We examined time course and inhibitor sensitivity
of myo-inositol, sorbitol, and glycerophosphorylcholine (GPC) accumulation
in MDCK cells exposed to hyperosmotic NaCl-, D-glucose-, or
mannitol-supplemented media. In NaCl medium, cells preferentially
accumulated inositol and GPC. In comparison, in glucose medium cells
preferentially accumulated sorbitol and GPC. Inositol demonstrated a late
(72-96 h) accumulation in glucose medium, although less than in NaCl
medium. Mannitol medium did not significantly stimulate accumulation of any
of these three osmolytes at 24 h, suggesting that hyperosmolality alone is
not sufficient stimulus for their accumulation in this time frame. GPC
accumulation was very rapid in glucose medium, and fell to the level
induced by NaCl medium at 96 h (approximately 50 nmol/mg protein). Inositol
and sorbitol accumulated more gradually, each reaching greater than 400
nmol/mg protein after 96 h. Sorbitol was still accumulating at 96 h,
whereas inositol plateaued at 72-96 h. Phlorizin or sorbinil blocked
accumulation of inositol or sorbitol, respectively. Sorbitol and GPC
accumulation in glucose medium were partially inhibited in absence of serum
or in presence of 1 microM vasopressin. Thus NaCl and glucose appear to
stimulate specific cellular mechanisms responsible for accumulation of
inositol, sorbitol, and GPC in MDCK cells. This accumulation is also
modulated by constituents of serum.
