Toluene metabolism in isolated rat hepatocytes: effects of in vivo pretreatment with acetone and phenobarbital

Abstract

Hepatocytes isolated from control, acetone- and phenobarbital-pretreated rats were used to study the metabolic conversion of toluene to benzyl alcohol, benzaldehyde, benzoic acid and hippuric acid at low (< 100 microM) and high (100-500 microM) toluene concentrations. The baseline formation rates of toluene metabolites (benzyl alcohol, benzoic acid and hippuric acid) were 2.9 +/- 1.7 and 10.0 +/- 2.3 nmol/mg cell protein/60 min at low and high toluene concentrations, respectively. In vivo pretreatment of rats with acetone and phenobarbital increased the formation of metabolites: at low toluene concentrations 3- and 5-fold, respectively; at high toluene concentrations no significant increase (acetone) and 8-fold increase (phenobarbital). Apparent inhibition by ethanol, 7 and 60 mM, was most prominent at low toluene concentrations: 63% and 69%, respectively, in control cells; 84% and 91% in acetone-pretreated cells, and 32% (not significant) and 51% in phenobarbital-pretreated cells. Ethanol also caused accumulation of benzyl alcohol. The apparent inhibition by isoniazid was similar to that of ethanol at low toluene concentrations. Control and acetone-pretreated cells were apparently resistant towards metyrapone; the decrease was 49% and 64% in phenobarbital-pretreated cells at low and high toluene concentrations, respectively. In these cells, the decrease in presence of combined ethanol and metyrapone was 95% (low toluene concentrations). 4-Methyl-pyrazole decreased metabolite formation extensively in all groups. Benzaldehyde was only found in the presence of an aldehyde dehydrogenase inhibitor. Increased ratio benzoic/hippuric acid was observed at high toluene concentrations. These results demonstrate that toluene oxidation may be studied by product formation in isolated hepatocytes. However, the influence of various enzymes in the overall metabolism could not be ascertained due to lack of inhibitor specificity.

Voltage‐dependent blockade of normal and mutant muscle sodium channels by benzylalcohol

“…At high concentrations of benzylalcohol, turnover is inhibited by the formation of enzyme–alcohol binary and abortive ternary complexes ( Shearer et al ., 1993 ). In addition, hepatic alcohol dehydrogenase substrate competition between benzylalcohol and ethanol may precipitate adverse metabolic interaction ( Messiha, 1991 ; Smith‐Kielland & Ripel, 1992 ). Although benzyl alcohol‐containing preparations are commonly used in intensive care units up to a possibly daily intake of 1 g die−1, little is known about the serum levels that are actually reached during long‐term parental administration.…”

Stability of toluene and reduction of acetone to 2-propanol in homogenates of the human liver, brain and lungs

“…In cases of longterm and improper storage of the autopsy material (blood and internal organs) the processes of toluene biodegradation [11][12][13][14] and conversion of acetone to 2-propanol [15] occur.…”

Effects of intraperitoneal application of toluene dissolved in propylene glycol on erythropoiesis in Wistar rats

“…Examination of the influence of toluene on health has been the subject of many studies, but with contradictory results and discrepancies concerning the interpretation of adverse effects (Pedersen and Rasmussen, 1982;Wang et al, 1996;Nedelcheva, 1996;Neghab and Stacey, 1997). It is known that toluene, as well as its metabolites, benzyl alcohol and hippuric acid, can induce oxidative stress and generate reactive oxygen (ROS) and nitrogen species (RNS) in the liver, CNS, lung, and kidney (Paguotto et al, 1967;Backes et al, 1993;Smith-Kielland et al, 1993), followed by consequent tissue damage (Mattia et al, 1993a;1993b, Tamizhselvi et al, 1995Hauffman et al, 1997;Myhre et al, 2001). However, data concerning the hematological toxicity of toluene are contradictory.…”