Serum T3 and T4 concentrations in the adult rats treated with herbicide 2,4-dichlorophenoxyacetic acid

The influence of sublethal doses of 2,4-dichlorophenoxyacetic acid (2,4-D) on serum T3 and T4 concentrations in Hsd Cpb: Wistar rats of both sexes was studied. The trial was performed on 24 males and females respectively, each divided into three groups of 8 animals (control, groups 1 and 2). Aqueous solution of the compound (11 mg/kg body weight--group 1 and 110 mg/kg body weight--group 2) or clean tap water (control group) was used. Aliquots of 2.4 ml/kg body weight were administered with a stomach tube from the 1st to 10th day of the experiment. Three days before the first treatment and on the 6th and 13th day of the experiment the serum T3 and T4 concentrations were determined by commercial radioimmunoassay kits (Byk-Sangtec Diagnostica), validated for rats. A significant decrease of serum T4 (P < 0.01) and T3 (P < 0.001) was determined in males of groups 1 and 2 during the experiment. On the 6th day of experiment serum T4 and T3 values were significantly lower (P < 0.001 and 0.01 respectively) in group 2 than in the controls and group 1 of both males and females. During the whole experiment serum T4 levels were lower in females than in males (P < 0.05).