Osmotic regulation of myo-inositol uptake in primary astrocyte cultures.
Uptake of myo-inositol by astrocytes in hypertonic medium (440 mosm/kg H2O) was increased near 3-fold after incubation for 24 hours, which continued for 72 hours, as compared with the uptake by cells cultured in isotonic medium (38 nmoles/mg protein). myo-Inositol uptake by astrocytes cultured in hypotonic medium (180 mosm/kg H2O) for periods up to 72 hours was reduced by 74% to 8 to 10 nmoles/mg protein. Astrocytes incubated in either hypotonic or hypertonic medium for 24 hours and then placed in isotonic medium reversed the initial down- or up-regulation of uptake. Activation of chronic RVD and RVI correlates with regulation of myo-inositol uptake. A 30 to 40 mosm/kg H2O deviation from physiological osmolality can influence myo-inositol homeostasis. The intracellular content of myo-inositol in astrocytes in isotonic medium was 25.6 +/- 1.3 micrograms/mg protein (28 mM). This level of myo-inositol is sufficient for this compound to function as an osmoregulator in primary astrocytes and it is likely to contribute to the maintenance of brain volume.
Isaacks
R E
RE
Research Laboratories, Veterans Affairs Medical Center, Miami, Florida 33125.
Bender
A S
AS
Kim
C Y
CY
Prieto
N M
NM
Norenberg
M D
MD
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D001692:Biological Transport; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism*; D006706:Homeostasis; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D007294:Inositol / Q000378:metabolism*; D007700:Kinetics; D009994:Osmolar Concentration; D051381:Rats; D013997:Time Factors
D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D007294:Inositol