Creatine as a compatible osmolyte in muscle cells exposed to hypertonic stress.
Exposure of C2C12 muscle cells to hypertonic stress induced an increase in cell content of creatine transporter mRNA and of creatine transport activity, which peaked after about 24 h incubation at 0.45 osmol (kg H(2)O)(-1). This induction of transport activity was prevented by addition of either cycloheximide, to inhibit protein synthesis, or of actinomycin D, to inhibit RNA synthesis. Creatine uptake by these cells is largely Na(+) dependent and kinetic analysis revealed that its increase under hypertonic conditions resulted from an increase in V(max) of the Na(+)-dependent component, with no significant change in the K(m) value of about 75 mumol l(-1). Quantitative real-time PCR revealed a more than threefold increase in the expression of creatine transporter mRNA in cells exposed to hypertonicity. Creatine supplementation significantly enhanced survival of C2C12 cells incubated under hypertonic conditions and its effect was similar to that obtained with the well known compatible osmolytes, betaine, taurine and myo-inositol. This effect seemed not to be linked to the energy status of the C2C12 cells because hypertonic incubation caused a decrease in their ATP content, with or without the addition of creatine at 20 mmol l(-1) to the medium. This induction of creatine transport activity by hypertonicity is not confined to muscle cells: a similar induction was shown in porcine endothelial cells.
Alfieri
Roberta R
RR
Department of Biochemistry, School of Life Sciences, JMS Building, University of Sussex, Brighton BN1 9QG, UK.
Bonelli
Mara A
MA
Cavazzoni
Andrea
A
Brigotti
Maurizio
M
Fumarola
Claudia
C
Sestili
Piero
P
Mozzoni
Paola
P
De Palma
Giuseppe
G
Mutti
Antonio
A
Carnicelli
Domenica
D
Vacondio
Federica
F
Silva
Claudia
C
Borghetti
Angelo F
AF
Wheeler
Kenneth P
KP
Petronini
Pier Giorgio
PG
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003401:Creatine / Q000493:pharmacokinetics / Q000494:pharmacology / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009122:Muscle Hypertonia / Q000503:physiopathology* / Q000517:prevention & control; D032446:Myoblasts / Q000187:drug effects / Q000502:physiology*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013552:Swine; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
D026901:Membrane Transport Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D011500:Protein Synthesis Inhibitors; D011506:Proteins; D012333:RNA, Messenger; C080679:creatine transporter; D003609:Dactinomycin; D012313:RNA; D000255:Adenosine Triphosphate; D003513:Cycloheximide; D003401:Creatine