Sevoflurane is biotransformed by guinea pig liver slices but causes minimal cytotoxicity.

Guinea pig liver slices were used to evaluate the biotransformation and hepatotoxic potential of sevoflurane. Precision-cut liver slices (250-300 microns thick) were incubated in sealed roller vials in buffer at 37 degrees C under 95% O2. Sevoflurane was added to produce 0.9 or 2.1 mM medium concentrations. After incubation (6-24 h), the intracellular K+ content and protein synthesis were determined, along with the defluorination of sevoflurane. Isoflurane was included for comparative purposes. Sevoflurane (2.1 mM) and isoflurane (2.3 mM) had no effect on slice K+ content, but both anesthetics depressed protein synthesis. The biotransformation of sevoflurane was maximal at 95% O2, with threefold more F- produced from sevoflurane than isoflurane. Sevoflurane appears to have a minimal effect on the guinea pig liver slices, which is consistent with in vivo studies in which minimal or no hepatotoxicity has been observed.

Effects of halothane and other volatile anaesthetics on protein synthesis and secretion in guinea pig liver slices.

We have investigated the effect of volatile anaesthetics on protein synthesis and secretion in Hartley male guinea pig liver slices. The slices (250-300 microns thick) were incubated in sealed roller vials containing Krebs-Henseleit buffer at 37 degrees C under 95% oxygen. Volatile anaesthetics were vaporized in the vials to produce constant concentrations in the medium. Halothane 1-2.1 mmol litre-1 produced a concentration-related decrease in protein synthesis (3H-leucine incorporation) and secretion. Deuterated halothane (d-halothane), which is less biotransformed, was less inhibiting than halothane: uptake of the 3H-leucine was not affected but its incorporation into the nascent peptide was inhibited. Enflurane 2.2 mmol litre-1, isoflurane 2.2 mmol litre-1 and sevoflurane 2.1 mmol litre-1 also inhibited protein synthesis, but to a lesser extent than halothane and d-halothane. We conclude that alterations in protein synthesis and secretion are an early and sensitive indicator of cellular injury by volatile anaesthetics in liver slices.

Minimal biotransformation and toxicity of desflurane in guinea pig liver slices.

Biotransformation and hepatotoxicity of desflurane were evaluated in the guinea pig liver slice culture system. Liver slices (250-300 microns) were prepared from 600-650-g male Hartley guinea pigs. The slices were incubated in sealed vials in a Krebs-Henseleit buffer at 37 degrees C under 95% O2. Desflurane was vaporized to produce media concentrations of 0.7-2.3 mM. After incubation (3-24 h) viability of the slices was determined (K+ content; protein synthesis secretion) along with the biotransformation of desflurane (F-). Isoflurane (2.3 mM) was included in the studies for comparative purposes. Although desflurane caused a mild concentration-related reduction in slice K+ content (1.1-2.2 mM; 20%-40% of control), the effects were less than those produced by 2.3 mM isoflurane (50% of control). High concentrations of desflurane decreased protein synthesis at the first 9 h of incubation, and isoflurane decreased protein synthesis throughout the incubation period. Neither anesthetic affected protein secretion. The biotransformation of desflurane was minimal with threefold less F- produced from desflurane than isoflurane.

Biotransformation of halothane in guinea pig liver slices.

The biotransformation of halothane was studied using liver slices. Precision-cut Hartley male guinea pig liver slices (1 cm diameter; 250-300 microns thick) were incubated in sealed roller vials containing supplemented Krebs-Henseleit buffer at 37 degrees C under different O2 tensions (2.5, 21, and 95%). After a 1-hr preincubation, halothane was vaporized in the vial producing a 1.9 mM medium concentration. Halothane metabolites (Br-, trifluoroacetic acid, F-) were measured at 2, 4, and 6 hr. Viability of the incubated slices was verified by determining intracellular K+ content and levels of cytochrome P-450, which were maintained under 95% O2 atmosphere but decreased with lower O2 tensions (2.5%). The highest fluoride production was 300 +/- 22 pmol/mg slice weight/6 hr at low O2 tension (2.5%). Defluorination decreased with increasing O2 tension to undetectable levels under 95% O2. Production of the oxidative metabolite, trifluoroacetic acid, was highest at 95% O2 (2.35 +/- 0.17 nmol/mg slice weight/6 hr). Trifluoroacetic acid production decreased with decreasing O2 tension. Br- production was the highest at 21% O2 (1.8 +/- 0.13 nmol/mg slice weight/6 hr). Production of Br- was not dependent on the O2 tension. The guinea pig slices are capable of biotransforming halothane (oxidative/reductive); therefore, this in vitro system appears suitable for studying the biotransformation of halothane.

Toxicity of halothane in guinea pig liver slices.

Guinea pigs have proven to be a reliable model of halothane associated hepatotoxicity. An in vitro system with Hartley male guinea pig liver tissue was designed to assess the toxicity of halothane and other volatile anesthetics in the target organ. Precision-cut guinea pig liver slices (250-300 microns) were incubated in sealed roller vials containing Krebs-Henseleit buffer (plus vitamins, amino acids, glutamine, gentamycin) at 37 degrees C, under 95%, 21% and 5% O2/CO2 atmospheres. Halothane (10-15 microliters) was injected through a Teflon septa cap on a filter paper wick and vaporized. Viability of the slices was monitored by measuring intracellular K+ content which was maintained under 95% O2 up to 24 h. A dose- and time-related decrease in intracellular slice K+ by 1.9, 2.1, 2.7 mM halothane in the media was observed. At 2.7 mM halothane a direct physio-chemical effect may be occurring since incubating liver slices from allylisopropyl-acetamide-treated animals did not protect against the drop in intracellular K+. Concentration/time responses of halothane, d-halothane, enflurane, isoflurane and sevoflurane were compared. Sevoflurane had no effect on the liver slice K+ content up to 24 h while the other anesthetics caused the following rank-order decrease in intracellular K+ content: halothane greater than isoflurane and enflurane greater than d-halothane. Precision-cut cultured guinea pig liver slices offer a system where the target tissue for intoxication by anesthetics can be examined for its susceptibility and mechanism of intoxication.