The effect of sodium nitrite on some parameters of the immune system

The effect of orally administered sublethal doses of 25. 50 and 100 mg/kg o f sodium nitrite in drinking water ad lib. for 21 days on the immune respon se of Balb/c mice was investigated. The immunological parameters were exami ned at three phases: 1 day (phase A), 1 week (phase B) and 3 weeks (phase C ) after the end of exposure to sodium nitrite. A significant decrease in do se-dependent manner was obtained in the following tests: lymphocyte percent ages, concanavalin A (Con A)- and lipopolysaccharide (LPS)-induced lymphocy te proliferation assessed by the colorimetric MTT method, natural killer (N K) cell activity against WEHI-164 target cells, as well as IgM and IgG tite rs against injected sheep erythrocytes. Maximum suppressions were obtained in phase A after treatment with sodium nitrite at 100 mg/kg including lymph ocyte count (17.5%), Con A-induced lymphocyte proliferation (40.1%), LPS-in duced lymphocyte proliferation (31.4%), IL-2-stimulated NK cell activity (5 9.2%), unstimulated NK cell activity (59.6%), IgM titer (57.5%) and IgG tit er (61.1%). On the other hand, a significant dose-dependent increase in neu trophil count (71.3%) in phase A and phagocytic activation (133%) in the fi rst two phases was obtained using the nitroblue tetrazolium (NBT) assay in the presence of phorbol myristate acetate (PMA). It was found that the immu nosuppressive effect of sodium nitrite is reversible after cessation of exp osure. (C) 2001 Elsevier Science Ltd. All rights reserved.