Immunotoxicological examination of repeated dose combined exposure by dimethoate and two heavy metals in rats

The immunotoxicity of 28 days combined oral exposure by dimethoate (DM) and two heavy metals (Pb or Cd) was investigated in male Wistar rats. Immunoto xic and no-effect doses of DM (28.2 and 7.04 mg/kg) were combined with immu notoxic and no-effect doses of CdCl2 (6.43 and 1.61 mg/kg) or lead acetate (80.0 and 20.0 mg/kg) in such a way that the high dose of each substance wa s given in combination with the no-effect dose of the other, To examine the interactions of these agents, general toxicological (body weight gain, org an weights), haematological (absolute and differential WBC, RBC, MCV, Ht, c ell content of the femoral bone marrow), and immune function (splenic PFC n umber, DTH reaction) parameters were measured. Treatment with the combinati on of Pb or Cd and DM did not result in a reduction of humoral (PFC) and ce llular (DTH) immune responses, whereas treatment with the substances alone did result in immune suppression, This protecting effect can probably be at tributed to an effect on the kinetics of the compounds tested father than o n the immune system itself, Further interactions were found in both combina tions, DM-Cd and DM-Pb, in the body weight gain and in the relative liver w eight; the DM-Pb combination also affected the relative thymus weight and t he MCV value, These findings show that the immunotoxic effects of the inves tigated materials, including their detectability and health consequences, c an be modified in case of combined exposure.