Adaptive response of Saccharomyces cerevisiae UEME3 to isoproturon depends on the presence of peptone in the rich culture medium

Abstract

The isoproturon, a herbicide which acts as a photosynthesis inhibitor is consider by some authors as toxic to humans having ability for tumors induction. When this phenylurea is metabolized by biotransformation systems can generate oxidative stress, activating electron transport chains present at mitochondria and endoplasmic reticulum and causing an increase of intracellular ROS. Having in account exposure above, the main purpose of this work was to compare the effects of isoproturon on cell growth, glutathione level and catalase T (CAT), glutathione peroxidase (GPx), alcohol dehydrogenase (ADH) and lactate dehydrogenase (LDH) activities of Saccharomyces cerevisiae UEME3, wildtype strain of Alentejo, Portugal, growing in YEPD, YED and YEP media. Cells at midexponential phase were inoculated in each medium and incubated during 72 h in a water bath with orbital stirring, at 28 ◦C, in the absence or presence of 100mM isoproturon. Samples from each treatment were used to obtain growth curves and to prepare post12,000×g supernatant, used for determination of GSH level as well as CAT T, GPx, ADH and LDH activities. The results show that isoproturon cause a significant increase of cell survival, GSH/GSSG ratio, LDH activities in yeast growing in presence of peptone plus glucose or peptone. Despite, isoproturon cause a decrease of CAT T and GPx ability to scavenger H2O2 or lipid hyroperoxides, it was also observed an increase of ADH activity in all media tested. The maintenance of high levels of GSH, as well as, the dehydrogenases responses can be interpreted as a stress adaptive mechanism to isoproturon where ADH and LDH are crucial enzymes for cytosolic NAD+ recycling.