Immunotoxicological effects of repeated combined exposure by cypermethrin and the heavy metals lead and cadmium in rats

The immunotoxic effect of a 28 days oral exposure by 55.4, 22.2, and 11.1 m g/kg cypermethrin (CY) was investigated in 4 weeks old male Wistar rats. Th e applied test system involved the determination of general toxicological p arameters (body weight gain, organ weight of thymus, heart, lung, liver, sp leen, kidneys, adrenals and the popliteal lymph node), haematological param eters (white blood cell count, red blood cell count, haematocrit, mean cell volume of red blood cells, cellularity of the femoral bone marrow), as wel l as immune function assays (splenic plaque forming cell assay, delayed typ e hypersensitivity reaction). The highest dose resulted in a significant in crease of the relative liver weight, and all three doses resulted in (altho ugh inconsistent) changes in the haematocrit and MCV values. The maximum of DTH reaction decreased at all three doses. On combination of the highest C Y dose with non-effective doses of lead or cadmium the immunotoxic effects of the former were modified. When immunotoxic doses of Cd or Pb were combin ed with the lowest CY dose, further interactions were observed on the exami ned parameters. The alterations of the immunotoxic effects of CY by simulta neous exposure with Cd or Pb, as described here, can lead to unexpected hea lth consequences and/or can lead to false positive or negative results in h uman epidemiological studies. (C) 1999 International Society for Immunophar macology. Published by Elsevier Science Ltd. All rights reserved.