Comparison of detection sensitivity of immuno- and genotoxicological effects of subacute cypermethrin and permethrin exposure in rats

Immuno- and genotoxicological effects of a 28-day oral treatment by equitox ic (1/10, 1/25, 1/50 LD50) doses of cypermethrin (55.4, 22.2, and 11.1 mg/k g) and permethrin (125.7, 50.3, and 12.6 mg/kg) were compared on male Wista r rats. Humoral and cell-mediated immunity were investigated by PFC assay a nd delayed type hypersensitivity (DTH) reaction (footpad swelling assay), a nd the genotoxic effects were studied by structural and numerical chromosom e aberrations in bone marrow cells. The experimental system also involved c ertain general toxicological (body weight gain, organ weights) and haematol ogical [white blood cell (WBC), red blood cell (RBC), haematocrit (Ht) and cell content of the femoral bone marrow] investigations. Among the immune f unction assays, only DTH reaction decreased at the two higher cypermethrin (CY) doses. These doses also increased the number of numerical chromosome a berrations of the bone marrow cells but did not change the number of struct ural aberrations. All CY doses decreased the mean cell volume (MCV) of RBCs and the Ht value. The two higher doses also reduced the WBC count in the p eripheral blood. Permethrin (PE), in the applied dose range, had no effect on the examined immune function parameters, but all three doses increased t he number of numerical chromosome aberrations. A dose-dependent increase in the liver weight, decreased MCV value, and elevated cell content of the fe moral bone marrow were also observed. Under these experimental conditions, examination of chromosome aberrations proved to be less sensitive in detect ion of exposure by cypermethrin than applied immune function assays did. Pe rmethrin, on the contrary, increased the number of numeric aberrations at a ll dose levels but had no effect on the immune function parameters examined . (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.