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, eac h 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 bod y weight - group 2) or clean tap water (control group) was used. Aliquots o f 2.4 ml/kg body weight were administered with a stomach tube from the 1(st ) to 10(th) day of the experiment. Three days before the first treatment an d on the 6(th) and 13(th) day of the experiment the serum T3 and T4 concent rations were determined by commercial radioimmunoassay kits (Byk-Sangtec Di agnostica), validated for rats. A significant decrease of serum T4 (P < 0.0 1) and T3 (P < 0.001) was determined in males of groups 1 and 2 during the experiment. On the 6(th) day of experiment serum T4 and T3 values were sign ificantly lower (P < 0.001 and 0.01 respectively) in group 2 than in the co ntrols and group 1 of both males and females. During the whole experiment s erum T4 levels were lower in females than in males (P < 0.05).