EFFECTS OF MILD CHRONIC HEAT EXPOSURE ON THE CONCENTRATIONS OF THIOBARBITURIC ACID REACTIVE SUBSTANCES, GLUTATHIONE, AND SELENIUM, AND GLUTATHIONE-PEROXIDASE ACTIVITY IN THE MOUSE-LIVER

To determine whether mild and chronic heat stress leads to oxidative s tress and to differenciate such effects of different exposure periods, we kept male ICR-mice at an ambient temperature of either 35 degrees C or 25 degrees C for 6 hours, 3 days, or 7 days and measured the conc entrations of thiobarbituric acid reactive substances (TEARS), glutath ione (GSH), selenium (Se), and glutathione peroxidase (GSH-Px) activit ies in the liver. Since the food consumption of the heat-exposed group was only half that of the control, we prepared pair-fed groups, which were kept at 25 degrees C and whose food consumption were limited to those of the heat-exposed group for the 3-day and the 7-day exposure. TBARS concentrations of the liver was significantly higher in the heat group than the control after the S-day exposure, while there was no s ignificant difference among the groups after the 7-day exposure. There was no significant difference in GSH concentrations between the heat- exposed group and the control after the 7-day exposure, when the GSH c oncentration of the pair-fed group was significantly lower than that o f the control. Hepatic cytosolic Se GSH-Px activity in the heat group was significantly less than that in the control group after the B-hour exposure and it tended to be lower in the heat group than that of the control group after the 7-day exposure, while there was no difference in the total GSH-Px activity among the three groups. Our results show ed that mild and chronic heat exposure may cause oxidative damage to o rganisms and that GSH-related anti-oxidative systems would play an imp ortant role to defensive reaction. (C) 1998 Tohoku University Medical Press.