LOCAL LYMPH-NODE ACTIVATION IN RATS AFTER DERMAL APPLICATION OF THE SENSITIZERS 2,4-DINITROCHLOROBENZENE AND TRIMELLITIC ANHYDRIDE

Five rat strains were compared for their performance in the local lymp h node assay (LLNA), a promising test system for the identification of the skin-sensitizing potential of chemicals in the mouse. The contact sensitizer 2,4-dinitrochlorobenzene (DNCB) and the contact and respir atory sensitizer trimellitic anhydride (TMA) were used as model chemic als and responses in rats were compared with those in BALB/c mice. The chemicals were applied to the dorsum of both ears, once daily for thr ee consecutive days; 2 days (mice) or 3 days (rats) thereafter, prolif erating cells were labelled by ip injection of BrdU 2 hr before the an imals were killed. Systemic effects were subsequently assessed by dete rmination of spleen, liver and kidney weights, skin effects by determi nation of swelling and inflammatory cell infiltration of the ears, and immune effects by determination of weight and proliferative activity of the local lymph nodes (LLN). Following application (x3) of DNCB or TMA, minor systemic effects were observed, as indicated by slightly el evated spleen and liver weights in a few rat strains and the mice. Ski n effects, consisting of increased ear thickness and presence of monon uclear inflammatory cell infiltrates, were observed in all rat strains treated with DNCB or TMA. LLN weights had increased, as had the proli ferative activity in these nodes. It was concluded that effects induce d by DNCB and TMA in all five rat strains were comparable with those i n mice.