Ethanol enhances ADP-ribosylation of protein in rat hepatocytes.
Decreases in hepatocyte NAD+ produced by ethanol are only partially explained by the increased conversion of NAD+ to NADH and NADP+. The purpose of this study was to determine whether a mechanism for the ethanol-induced decrease in NAD+ is its increased use in ADP-ribosylation. Exposure of hepatocytes in culture for 2 hr to 100 mmol/L ethanol increased the incorporation of 14C-ribose from prelabeled NAD+ into 14C-ribosylated proteins. Poly (ADP-ribose) polymerase activity was increased by exposure of isolated hepatocytes to 100 mmol/L ethanol for 10 min. In hepatocyte culture, increases in poly (ADP-ribose) polymerase were not detected after exposure to 100 mmol/L ethanol for 10 min or 2 hr but rather occurred at 24 hr. Ethanol exposure of hepatocytes in culture for 2 hr, however, decreased the Km for NAD+ of poly (ADP-ribose) polymerase. Both nicotinamide and 5-aminobenzamide, which are inhibitors of poly (ADP-ribose) polymerase, prevented the decrease in NAD+ produced by 2-hr exposure of hepatocytes in culture to 100 mmol/L ethanol. The effect of ethanol in decreasing DNA synthesis on days 3 and 4 of culture was not reversed by the inhibitors of poly (ADP-ribose) polymerase. These results indicate that increased ADP-ribosylation of hepatocyte proteins is a mechanism for the effect of ethanol in decreasing NAD+.
Akinshola
B E
BE
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Sharma
S
S
Potter
J J
JJ
Mezey
E
E
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D002469:Cell Separation; D004247:DNA / Q000096:biosynthesis; D000431:Ethanol / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D009243:NAD / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D011506:Proteins; D009243:NAD; D000246:Adenosine Diphosphate Ribose; D000431:Ethanol; D004247:DNA