Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on liver, thymus and cell proliferation in popliteal lymph nodes after foot pad injection of streptozotocin in rats

Immunosuppressive substances can reduce the cell proliferation in the popliteal lymph node of rats induced by foot pad injection of, e.g., streptozotocin. We investigated the effect of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) in such an experimental set-up. One week before streptozotocin was injected into the right foot pad (5 mg/40 μl) the rats were treated with a single s.c.-injection of 3 μg 14C-TCDD/kg body wt or with the vehicle only (toluene/DMSO). One week after the injection of streptozotocin the weight of the right and left lymph nodes as well as the cell number of both lymph nodes were determined after disintegration in phosphate buffered salien. The quotients of the results obtained from the right and the left lymph node (“index”) were calculated. Relevant organs were weighed and the TCDD concentrations in liver, fat and thymus were measured by scintillation counting. Using cyclophosphamide or cyclosporine A as “positive control” we found a clear-cut reduction of the cell index to values less than 10% of the vehicle controls. Systemic treatment with TCCD, however, at a dose which caused an increase in liver weight and a decrease in thymus weight, did not influence the increase of cells in the popliteal lymph node in rats induced by foot pad injection of steptozotocin.