Immuno- and neurotoxicological investigation of combined subacute exposure with the carbamate pesticide propoxur and cadmium in rats

In the present study, the effects of subchronic per os exposures to cadmium chloride (CdCl2), and a carbamate insecticide, propoxur (Pr), were investigated in male Wistar rats on general toxicological (body weight gain, relative organ weights) haematological (RBC, WBC, Ht, MCV, cell content of the femoral bone marrow) immune function (plaque forming cell (PFC) assay, delayed type hypersensitivity (DTH) reaction) and neurotoxicological (spontaneous and stimulus-evoked cortical activity, nerve conduction velocity) parameters. The animals were treated for 4, 8 and 12 weeks with 6.43 mg/kg CdCl2, 8.51 mg/kg Pr, or with a combination of 6.43 mg/kg CdCl2+0.851 mg/kg Pr or 8.51 mg/kg Pr+1.61 mg/kg CdCl2. Cadmium exposure affected the relative thymus, liver, and adrenal weight, RBC count, haematocrit and MCV, and there was an increase in nerve conduction velocity and a decrease in the cortical evoked potential latency. Pr induced a decrease in thymus weight, had some effect on the liver weight but none on the electrophysiological parameters. A significant interaction between Cd and Pr was detected by the following parameters: RBC, Ht, PFC, and nerve conduction velocity. The results indicate that combined exposures in humans may result in a shift in the apparent detection limits and/or in the LOEL of the single substances. The latter raises the necessity to reconsider exposure limits in situations where the risk of combined exposure is high. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.