Defective translocation of PKCepsilon in EtOH-induced inhibition of Mg2+ accumulation in rat hepatocytes.
BACKGROUND
Rats chronically fed ethanol for 3 weeks presented a marked decreased in total hepatic Mg(2+) content and required approximately 12 days to restore Mg(2+) homeostasis upon ethanol withdrawal. This study was aimed at investigating the mechanisms responsible for the EtOH-induced delay.


METHODS
Hepatocytes from rats fed ethanol for 3 weeks (Lieber-De Carli diet-chronic model), rats re-fed a control diet for varying periods of time following ethanol withdrawal, and age-matched control rats fed a liquid or a pellet diet were used. As acute models, hepatocytes from control animals or HepG2 cells were exposed to varying doses of ethanol in vitro for 8 minutes.


RESULTS
Hepatocytes from ethanol-fed rats presented a marked inhibition of Mg(2+) accumulation and a defective translocation of PKCepsilon to the cell membrane. Upon ethanol withdrawal, 12 days were necessary for PKCepsilon translocation and Mg(2+) accumulation to return to normal levels. Exposure of control hepatocytes or HepG2 cells to a dose of ethanol as low as 0.01% for 8 minutes was already sufficient to inhibit Mg(2+) accumulation and PKCepsilon translocation for more than 60 minutes. Also in this model, recovery of Mg(2+) accumulation was associated with restoration of PKCepsilon translocation. The use of specific antisense in HepG2 cells confirmed the involvement of PKCepsilon in modulating Mg(2+) accumulation.


CONCLUSIONS
Translocation of PKCepsilon isoform to the hepatocyte membrane is essential for Mg(2+) accumulation to occur. Both acute and chronic ethanol administrations inhibit Mg(2+) accumulation by specifically altering PKCepsilon translocation to the cell membrane.
Torres
Lisa M
LM
Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4970, USA.
Konopnika
Bocena
B
Berti-Mattera
Liliana N
LN
Liedtke
Carole
C
Romani
Andrea
A
D000818:Animals; D016375:Antisense Elements (Genetics) / Q000494:pharmacology; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D000431:Ethanol / Q000008:administration & dosage / Q000494:pharmacology*; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D051744:Protein Kinase C-epsilon / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D016375:Antisense Elements (Genetics); D000431:Ethanol; D051744:Protein Kinase C-epsilon; D008274:Magnesium