The effects of acute ethanol exposure on inhibitors of hepatic regenerative activity in the rat.

The purpose of this study was to identify the mechanism(s) whereby acute ethanol exposure inhibits hepatic regenerative activity in the rat. Adult, male, Sprague-Dawley rats (200-250 g) were randomized to receive either ethanol (1 g/kg i.p. q 4 h) or an equal volume of saline (controls) for 24 h beginning 1 h prior to a 70% partial hepatectomy (PHx). At 0, 3, 6, 12 and 24 h post-PHx, rats were sacrificed (N = 4-6/group), and the expression of the following genes associated with inhibition of hepatocyte proliferation were documented; p53, p21, transforming growth factor-beta1 (TGF-beta1) and gamma aminobutyric acid transport protein (GABA-TP). Inhibition of hepatic regenerative activity was confirmed by 3H-thymidine incorporation into hepatic DNA at 24 h post-PHx. The results of the study revealed that in ethanol-treated rats, DNA synthesis was inhibited by 37% when compared to saline-treated controls (p < 0.01). Regarding suppressor gene expression, both p21 and TGF-beta1 mRNA expression in ethanol-treated rats were similar to those obtained in saline-treated controls. Although p53 mRNA expression differed in the two groups, in the ethanol-treated group, p53 mRNA expression was decreased rather than increased (relative to controls) at 24 h post-PHx, a finding not in keeping with inhibition of DNA synthesis. GABA-TP mRNA was strongly expressed prior to PHx in both ethanol- and saline-treated rats. Following PHx, GABA-TP mRNA expression decreased in both groups but remained low in the saline-treated group while returning to pre-PHx values in ethanol-treated rats. In summary, the results of this study indicate that the inhibitory effects of ethanol on hepatic regeneration are not associated with significant or the appropriate changes in mRNA expression of the p53, p21 or TGF-beta1 suppressor genes. On the other hand, transcriptional changes in GABA-TP gene expression post-PHx are in keeping with an inhibitory effect of GABA on hepatic regeneration.