Immunotoxicological investigations on rats treated subacutely with dimethoate, As3+ and Hg2+ in combination

Effects of combined exposure with dimethoate (DM), HgCl2 (Hg), and NaAsO2 ( As) were investigated following a 28-day oral exposure in male Wistar rats. In preliminary experiments, the LOEL (Lowest Observed Effect Level) and NO EL (Non Observed Effect Level) doses of the substances were determined usin g the same experimental system [determination of body weight gain, organ we ights of brain, thymus, heart, lung, kidneys, adrenals, spleen, testicles, popliteal lymph node, white blood cell (WBC) and red blood cell (RBC) count , haernatocrit (Ht), mean cell volume (MCV) of RBCs, cell content of the fe moral bone marrow, IgM-plaque forming cell (PFC) content of the spleen, del ayed type hypersensitivity (DTH) reaction] and animal strain. In the combin ation studies, LOEL dose of DM (28.2 mg/kg) was combined with NOEL doses of the heavy metals (HgCl2 = 0.40 mg/kg, NaAsO2 = 3.33 mg/kg), and vice versa (DM = 7.04 mg/kg, HgCl2 = 3.20 mg/kg, NaAsO2 = 13.3 mg/kg). In the DM-Hg c ombinations, significant alterations were found versus the corresponding hi gh-dose internal control in the body weight gain, relative liver and kidney weights, and in the PFC response. When DM was combined with As, interactio ns were indicated by changes of relative liver weight, MCV value, and the P FC content of the spleen.