The involvement of some low-molecular thiol compounds in the mechanisms of peroxidative action of cadmium (Cd) and ethanol (EtOH) was studied. Concentrations of reduced glutathione (GSH), metallothionein (Mt) and thiol (-SH) groups in protein and non-protein fractions were assessed in the homogenates of the liver and kidney of rats exposed to Cd (50 Cd/dm³ of drinking water) and EtOH (5 g EtOH/kg body weight/24 h, intragastrically), singly or in combination, for 12 weeks.
Exposure to Cd caused a reduction in the concentration of GSH and non-protein SH groups in the liver and kidneys with a simultaneous increase in Mt level in these organs. The concentration of total SH groups increased only in kidneys. Administration of EtOH had no effect on Mt concentration in both organs, but caused a reduction in the concentration of GSH and non-protein SH groups. A reduction in the level of total SH groups following exposure to EtOH was also noted in the liver. In the group of rats with a simultaneous exposure to Cd and EtOH, GSH concentration was decreased in the liver compared to the control and Cd-exposed animals, and in the kidney in comparison to the control and EtOH-receiving rats. Following the combined exposure to Cd and EtOH, the concentration of non-protein SH groups decreased in the liver and kidneys in comparison to the control and Cd-exposed rats, and in the liver also in comparison to the EtOH group. Mt concentration increased in the liver and kidneys of animals exposed to a combination of Cd and EtOH, compared to the control and EtOH group, but was reduced compared to the Cd group. Combined administration of Cd and EtOH caused an increase in the concentration of total SH groups in the kidneys compared to the control, Cd and EtOH groups. A negative correlation was found between GSH concentration and malondialdehyde (MDA) levels and positive correlation between Mt and MDA.
The intensity of lipid peroxidation as well as GSH and Mt concentrations influencing this process in the state of combined exposure to Cd and EtOH results both from independent actions of these substances and interactions between them.
The study outcome seems to indicate that the Cd- and EtOH-induced reduction in GSH and non-protein SH groups in the liver and kidneys may be one of the mechanisms that leads to lipid peroxidation in these organs.