Ketone potentiation of haloalkane-induced hepatotoxicity: CCl4 and ketone treatment on hepatic membrane integrity.

Previous results in male Sprague-Dawley rats indicate that acetone (A), methyl ethyl ketone (MEK), and methyl isobutyl ketone (MiBK) pretreatments (3 d, p.o.) at a dosage of 6.8 mmol/kg potentiate CCl4 hepatotoxicity. The potentiation potency profile observed was MiBK > A > MEK. In the present study, male Sprague-Dawley rats were treated for 3 d with 6.8 mmol/kg (p.o.) of A, MEK, or MiBK using Emulphor as vehicle (10 ml/kg). Rats were either killed 18 h after the last pretreatment or treated with CCl4 (prepared in corn oil) and then killed 48 h later. Livers were perfused; purified plasma membrane (PM), sinusoidal (SM) and basal canalicular membrane (BCM) fractions were prepared. Membrane fluidity was monitored by fluorescence polarization using 1,6-diphenyl-1,3,5-hexatriene (DPH) or 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH). The following membrane enzymes were measured to monitor membrane purity and treatment effects: 5'-nucleotidase (5N), leucine aminopeptidase (LAP), and alkaline phosphatase (AP). Our results suggest that CCl4 modifies membrane integrity as indicated by a decrease in liver membrane 5N, LAP, and AP activity. CCl4 also increased the fluidity of the lipid and protein portions of the liver membranes as measured by the DPH and TMA-DPH fluorescence probes, respectively. Of the three ketones, only A altered CCl4 effects on plasma membrane enzymes and decreased BCM fluidity. The data only partially support increased susceptibility of liver membranes by ketone pretreatment as a factor implicated in the mechanism of potentiation of CCl4-induced hepatotoxicity.