Magnesium sulfate induces translocation of protein kinase C isoenzymes alpha and delta in myometrial cells from pregnant women.
OBJECTIVE
The purpose of this study was to determine the effect of magnesium sulfate on protein kinase C (PKC) translocation in myometrial cells from pregnant women.


METHODS
Myometrium was obtained at the time of cesarean delivery from women at term before labor. Cultured myometrial cells were treated with magnesium sulfate (3, 5, and 10 mmol/L), oxytocin (0.1 micromol/L), or 12-O-tetradecanoylphorbol-13-acetate (TPA, 0.1 micromol/L). The translocation of PKC isozymes alpha (calcium dependent) and delta (calcium independent) from cytosol to membrane fractions was assessed with use of Western blot analysis.


RESULTS
In unexposed control cells, the majority of PKC alpha and delta was located in the cytosol fraction. Exposure to magnesium sulfate for 60 minutes induced translocation of both PKC alpha and delta at concentrations as low as 5 and 3 mmol/L, respectively. The magnitude of magnesium sulfate induced translocation for PKC delta is similar to that seen after oxytocin or TPA exposure but less for PKC alpha. Exposure to oxytocin for 30 minutes and 60 minutes induced translocation of PKC alpha and delta, respectively. Exposure to TPA for 5 and 30 minutes induced translocation of PKC alpha and PKC delta, respectively. In calcium-free media, only TPA induced translocation of these two isoenzymes.


CONCLUSIONS
Magnesium sulfate stimulates PKC translocation in cultured myometrial cells from pregnant women. Magnesium sulfate and oxytocin require extracellular calcium to induce translocation of both PKC alpha and delta.
Bermeo
Miguel E
ME
Departments of Obstetrics and Gynecology, Indiana University School of Medicine, Indianapolis, IN, USA.
Fomin
Victor P
VP
Ventolini
Gary
G
Gibbs
Shawn G
SG
McKenna
David S
DS
Hurd
William W
WW
D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008278:Magnesium Sulfate / Q000494:pharmacology*; D009215:Myometrium / Q000166:cytology* / Q000378:metabolism; D011247:Pregnancy; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta
D007527:Isoenzymes; D008278:Magnesium Sulfate; C496628:PRKCA protein, human; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta