Effect of dibutyryl cyclic AMP on the kinetics of myo-inositol transport in cultured astrocytes.
Dibutyryl cyclic AMP (dBcAMP) is known to induce maturation and differentiation in astrocytes. As myo-inositol is an important osmoregulator in astrocytes, we examined the effects of maturation and biochemical differentiation on the kinetic properties of myo-inositol transport. Treatment of astrocytes with dBcAMP significantly decreased the Vmax of myo-inositol uptake, but the effect on Km was not significant. The myo-inositol content of astrocytes was significantly decreased in cells treated for 5 days with dBcAMP as compared with untreated controls. Maximum suppression of myo-inositol uptake occurred 7 days after exposure of astrocytes to dBcAMP; this was gradually reversible when dBcAMP was removed from the medium. After exposure to hypertonic medium for 6 h, mRNA expression of the myo-inositol co-transporter was diminished by approximately 36% in astrocytes treated with dBcAMP as compared with untreated cells. It appears that myo-inositol transporters in astrocytes treated with dBcAMP are either decreased in number or inactivated during maturation and differentiation, suggesting that the stage of differentiation and biochemical maturation of astrocytes is an important factor in osmoregulation.
Isaacks
R E
RE
Veterans Affairs Medical Center and Department of Medicine, University of Miami School of Medicine, Florida 33125, USA.
Bender
A S
AS
Reuben
J S
JS
Kim
C Y
CY
Shi
Y F
YF
Norenberg
M D
MD
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D015152:Blotting, Northern; D003994:Bucladesine / Q000008:administration & dosage / Q000494:pharmacology*; D002352:Carrier Proteins / Q000235:genetics; D002454:Cell Differentiation; D002478:Cells, Cultured; D003470:Culture Media; D015870:Gene Expression; D006360:Heat-Shock Proteins / Q000235:genetics; D006982:Hypertonic Solutions; D007294:Inositol / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D027981:Symporters
D002352:Carrier Proteins; D003470:Culture Media; D006360:Heat-Shock Proteins; D006982:Hypertonic Solutions; D008565:Membrane Proteins; D012333:RNA, Messenger; D027981:Symporters; C073884:SLC5A3 protein, human; D007294:Inositol; D003994:Bucladesine