Free radical processes in the liver mitochondria of rats exposed to diethyl phthalate

Abstract

Diethyl phthalate (DEF) is a synthetic chemical widely used as plasticizer and additive in personal care and pharmaceutical products. Low-dose exposure to this xenobiotic over a long period contributes to its intake into the human body in a high doses. To date, studies of DEF influence on free radical processes in liver cells, in which it is not only metabolized but can also have a prooxidant effect, remain limited. The aim of our research was to determine ROS formation, the intensity of oxidative modification of proteins (OMP) and proteolytic activity in the mitochondrial fraction of liver tissue of rats exposed to diethyl phtalate. The experimental white outbred rats were divided into three groups: I – intact animals (control), II and III – rats administered DEF orally for three weeks at a doses that reflect the dose levels received by humans, namely 2.5 and 5.4 mg/kg b.w. respectively. The animals were euthanized on the 14th and 21st day after xenobiotic administration. The mitochondrial fraction from the rat liver was isolated and the level of superoxide and hydroxyl radicals, protein carbonyl derivatives, SH-groups and Schiff bases was determined. Proteolytic activity was assessed in the test of hemoglobin cleavage. It was shown that administration of DEF in a dose of 2.5 mg/kg initiated ROS generation and OMP intensification in the rat liver mitochondria only with prolonged administration for 21 days, whereas its administration in a dose of 5.4 mg/kg led to intensification of these processes already on day 14th followed by further amplification on day 21st. The activity of proteolytic enzymes in the mitochondrial fraction was found to be depended on the degree of DEF–induced OMP and was increased with minor OMP intensification but decreased with significant intensification of proteins free radical oxidation. Keywords: carbonyl derivatives, diethyl phthalate, liver, mitochondrial fraction, proteolytic enzymes, ROS, SH-groups