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) pretrea tments (3 d, po) at a dosage of 6.8 mmol/kg potentiate CCl4 hepatotoxi city. 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 (po) of A, MEK, or MiBK using Emulphor as vehicle (10 ml/ kg). Rats were either killed 18 h after the last pretreatment or treat ed with CCl4 (prepared in corn oil) and then killed 48 h later. Livers were perfused; purified plasma membrane (PM), sinusoidal (SM) and bas al canalicular membrane (BCM) fractonss were prepared. Membrane fluidi ty was monitored by fluorescence polarization using 1,6-diphenyl-1,3,5 hexatriene (DPH) or trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatrien e (TMA-DPH). The following membrane enzymes were measured to monitor m embrane purity and treatment effects: 5'nucleotidase (5N), leucine ami nopeptidase (LAP), and alkaline phosphatase (AP). Our results suggest that CCl4 modifies membrane integrity as indicated by a decrease in li ver membrane 5N, LAP, and AP activity. CCl4 also increased the fluidit y of the lipid and protein portions of the liver membranes as measured by the DPH and TMA-DPH fluorescence probes, respectively. Of the thre e ketones, only A altered CCl4 effects on plasma membrane enzymes and decreased BCM fluidity. The data only partially support increased susc eptibility of liver membranes by ketone pretreatment as a factor impli cated in the mechanism of potentiation of CCl4-induced hepatotoxicity.