MAST-CELL RECOVERY FOLLOWING CHRONIC TREATMENT WITH COMPOUND-48 86/

Histochemical and functional properties of mast cells (MC) in Brown No rway rats recovering from chronic treatment with the MC secretagogue c ompound 48/80 were examined. In the skin, treatment for 5 days with co mpound 48/80 resulted in a marked decrease in MC subpopulations define d by differential alcian blue/safranin staining. Both safranin-positiv e connective tissue MC and alcian blue staining MC were reduced in num ber. This was accompanied by significant decreases in skin histamine a nd rat MC serine protease I contents and a loss of specific IgE-mediat ed passive cutaneous anaphylaxis (PCA) activity. The PCA reaction did not return to normal before 2 months after stopping treatment and only when the numbers of safranin-positive connective tissue MC and skin h istamine content reached pretreatment levels. The subepidermal alcian blue staining MC not eliminated by the compound 48/80 treatment were f ormalin resistant (unlike alcian blue staining mucosal MC of the intes tine) and apparently played no role in the PCA response. MC numbers, h istamine levels, and rat MC serine protease I content of the tongue we re similarly decreased by compound 48/80. In contrast, mucosal MC of t he gut were unaffected by the secretagogue treatment.