In Vitro Increase of Histidine Decarboxylase Activity and Release of Histamine by Peritoneal Resident Cells of Mast Cell-Deficient W/Wv Mice; Possible Involvement of Macrophages

When peritoneal resident cells (PRCs) of genetically mast cell-deficient WBB6F1 - W/Wv mice were cultured in vitro for 5 h at 37°C, their histidine decarboxylase [HDC, L-histidine carboxylyase, E.C. 4.1.1.22] activity increased 10-fold. Since inhibitors for energy production and mRNA and protein syntheses inhibited this increase of HDC activity, it appeared to represent de novo synthesis of the enzyme, i.e., induction. This increase was followed by an increase in the amount of histamine in the culture medium of the cells, indicating that histamine synthesized by the induced HDC was not stored in the cells but was quickly released. Mast cells were not involved in the HDC induction, because the extents of HDC induction in PRCs of W/Wv and wild type +/+ mice were similar. The removal of T cells with anti-Thy-1,2 antibody and complement from the PRCs did not affect the HDC induction, but the removal of phagocytes decreased the induction to one-tenth in spite of a 2-fold increase in the proportion of B cells in the PRCs. After separation of the PRCs into adherent and non-adherent fractions, the increase in HDC activity was found to be associated with the adherent fraction that was mostly positive to esterase staining. These results suggest that HDC was induced in peritoneal macrophages.