Toxicity of Na 251CrO 4 when used to label rat lymphocytes

Abstract

Lymphocytes preincubated with various activities of Na 2 51CrO 4 were tested for their ability to induce a local, popliteal lymph node graft-versus-host (GVH) reaction. Incubation with 100 μCi of the isotope per ml of cell suspension impaired the GVH activity, 25 μCi gave a reduced response in 1 out of 3 experiments, whereas 10 μCi had no effect. The reduced GVH response was due to radiation rather than chemical damage of the cells. Preincubation of the cells with either cold Na 2CrO 4 or outdated Na 2 51CrO 4 with concentrations of Cr identical to the ones used to label cells with 100 μCi/ml cells did not impair the GVH reactivity. The cellular uptake of Na 2 51CrO 4 showed first-order kinetic over wide concentrations ranges. Mitomycin C-treated lymphocytes showed a more heavily depressed GVH reactivity than would be expected from their moderately reduced ability to accumulate in the lymph nodes. It is recommended that doses of Na 2 51CrO 4 in excess of 10 μCi/ml cells should not be used for functional studies of lymphocytes.