Rat Liver Slices and Diazepam Metabolism: In Vitro Interactions With Volatile Anaesthetic Drugs and Albumin †

Abstract

The influence of the volatile anaesthetic agents enflurane, isoflurane, halothane and the halothane metabolite trifluoroacetic acid was studied on the hepatic elimination of diazepam, by incubating precision-cut slices of rat liver in a closed system. The impact of anaesthetic-induced action on enzyme activity and diazepam binding to human serum albumin (HSA) was assessed in protein free and protein containing buffers, respectively. Human serum albumin reduced the elimination of diazepam by 12 and 50% at concentrations of 1 and 10 mg ml-1, respectively. In the absence of albumin, halothane 1 mmol litre-1 reduced the elimination of diazepam by 13%, whereas enflurane at 1.5 mmol litre-1 caused a reduction of 8%. No effect was seen from isoflurane 1 mmol litre-1 and trifluoroacetic acid 4 mmol litre-1. In the presence of the highest concentration of albumin, however, an increased elimination of diazepam of 24% resulted from exposure to enflurane and trifluoroacetic acid, while no statistically significant changes were seen for isoflurane and halothane. The present work supports the view that volatile anaesthetic agents may cause pharmacokinetic drug interactions by interference with both enzyme activity and drug protein binding.

Use of Precision-Cut Liver Slices as an In Vitro Tool for Evaluating Liver Function

“…Precision-cut liver slices are an outstanding in vitro system for studying xenobiotic disposition (14,21,29,38). On a per-weight basis, liver slices biotransform virtually equivalent to a perfused liver model system (11). More importantly, they perform integrated Phase I and Phase II biotransformation as would be seen in vivo (1,27).…”

Contributions of Liver Perfusion Flow Rate and Enzyme Inhibition to Altered Verapamil Clearance With Halothane

“…This system is valuable in that it permits separation of hepatic flow and hepatic enzyme inhibition properties with anesthetic administration; it will prove useful for evaluating other drug-drug interactions. The perfusate used for our study was devoid of added protein, and therefore effects such as alterations in protein binding could not be evaluated (12). Additionally, the hepatic perfusion rate that we utilized for our "reduced flow group" was necessarily chosen from previously obtained results in the literature.…”

Rat Liver Slices: Metabolic Changes During Short Time Incubation in Glucose‐Free Buffer

“…Short-time (2 hr) rat liver slice incubation in glucose-free medium has been used to study drugdrug interactions where degree of drug protein binding was one of the determinants for altered drug elimination. Drug binding to proteins in vitro is generally determined in buffers devoid of glucose (Dale et al 1988). A confirmation that rat liver slices are able to utilize endogenous energy sources to meet the metabolic requirements during incubation in a closed system without glucose supplementation was therefore needed.Non-induced, non-fasted male Sprague-Dawley rats (225-300 g) from Merllegaard (Denmark) were sacrificed by decapitation.…”

“…After 30 min. of preincubation (Dale et al 1988), the inserts were moved to a new vial containing buffer, gassed and incubated for 4 hr. pH, carbon dioxide tension (pC0,) and oxygen tension (PO,) in the buffer were measured on a Radiometer blood gas machine (ABL 330).…”