Pharmacological and Morphological Changes in Rat Mast Cells Exposed to Nitrogen Dioxide in Vitro

Abstract

In spite of important roles that mast cells play in inflammation, immunoregulation, and immediate hypersensitivity, the effects of environmental pollutants on mast-cell activity are little known. Our purpose in this study is to investigate the effects of in vitro exposure to nitrogen dioxide (NO₂) on histamine and O-hexosaminidase release from rat peritoneal mast cells (PMC). Purified PMC were exposed to 5 and 20 ppm NO₂ in vitro for 30 or 60 min. The numbers of PMC decreased significantly after 60 min of exposure to 20 ppm NO, but not after 30 min of exposure to NO₂ Significant spontaneous histamine release was not observed in the 30-min exposure. However histamine release by compound 48/80 or substance P from NO₂-exposed mast cells was markedly inhibited compared with that from the controls, but the inhibition was not observed in histamine release by ionophore A23187. β-Hexosaminidase release by substance P from NO₂-exposed mast cells was significantly inhibited. Morphological observation showed the effect on the cell surface of Norexposed mast cells. These results suggest that NO₂ may affect mast-cell activity through damage to its membrane.