Modulation of phenobarbitone-induced loss of gap junctional intercellular communication in hepatocyte couplets

Phenobarbitone (PB) produced a dose- and time-dependent decrease in gap junctional intercellular communication (GJIC) (up to 25.0 +/- 5.3% inhibition) in rat hepatocyte couplets (4 h cultures). The effect was reversible and independent of protein synthesis. This inhibition was exacerbated (to 53.3 +/- 5.4% inhibition) by depletion of intracellular glutathione following pretreatment with diethylmaleate (0.5 microM, 15 min). Inhibition was also significantly enhanced by addition of the cytochrome P450 inhibitors SKF 525A (25 microM) and metyrapone (20 nM). In contrast, hepatocyte couplets derived from rats pretreated with PB (0.1% w/v in drinking water) for up to 28 days were fully functional regarding GJIC and were found to be refractory to the effects of PB added in vitro. This, coupled with the lack of effect of p-hydroxy-PB, suggests that an active metabolite of PB is not involved in the inhibition of GJIC which may, instead, be through an oxidative stress, which is prevented by glutathione.