Background: Poly-adenosine diphosphate (ADP)-ribosylation is involved in a variety of biological processes, which include DNA repair, malignant transformation, and apoptosis. It is of interest how this reaction is altered after long-term alcohol intake. Therefore, we determined long-term alcohol effects on hepatic poly-ADP-ribosylation in the rat.
Methods: Male Sprague Dawley(R) rats (four pairs) were pair-fed a nutritionally adequate liquid diet that contained ethanol as 36% of total energy and an isocaloric control diets for 4 weeks. Liver tissue homogenates and nuclear fractions were subjected to ADP-ribosylation with [32P]nicotinamide adenine dinucleotide. The ADP-ribosylated proteins were separated by SDS-PAGE, followed by autoradiography. Expression of poly-ADP-ribose polymerase (PARP) also was evaluated by Western blotting.
Results: Incubation of rat liver homogenates in ADP-ribosylation reaction mixture resulted in a radiolabeling of a 116 kDa protein, most likely auto-ribosylation of PARP. This poly-ADP-ribosylation was increased significantly (p < 0.025) after long-term alcohol intake. This alcohol effect was reproducible in nuclear fractions as well. Expression levels of PARP, however, were comparable between alcohol-fed rats and their pair-fed controls.
Conclusion: Poly-ADP-ribosylation, an important posttranslational modification of nuclear proteins, was increased significantly after chronic alcohol consumption in the rat.