Differential release of histamine and prostaglandin D₂ in rat peritoneal mast cells activated with peptides

Rat peritoneal mast cells co-cultured with mouse 3T3 fibroblasts (MC/3T3) are fully responsive to immunologic stimuli. To assess their nonimmunologic activation MC/3T3 were challenged with various peptides. Optimal concentrations of substance P(10^-4 M) and bradykinin (5 × 10^-5 M) induced histamine release of 58.2 ± 9.3 and 66.8±6.6%, respectively, while neurotensin (10^-4 M) released only 16.6±3.7% histamine. Freshly isolated mast cells (F-MC) challenged with the same concentrations of peptides released lower percentages of histamine (substance P 45.6 ± 5.1%, bradykinin 32.5 ± 5.3%, neurotensin 11.3 ±6.0%). In both MC/3T3 and F-MC, only minute amounts of prostaglandin D₂(PGD₂) were produced. In contrast, activation with anti-IgE antibodies and compound 48/80 caused both histamine release and PGD₂ generation. Compound 48/80-stimulated MC/3T3 and F-MC released 80.2±3.4 and 51.8±6.2% histamine, respectively, and produced 15.4 ± 2.8 ng/10⁶ mast cells and 3.9 ± 1.4 ng/10⁶ mast cells PGD₂, respectively. These findings indicate that peptides and bradykinin induce selective release of histamine with no PGD2 production in both F-MC and MC/3T3. Moreover, MC/3T3 preserve their functional characteristics of connective tissue mast cells since they are fully responsive to these peptides as F-MC.