Differential release of histamine and prostaglandin D 2 in rat peritoneal mast cells: roles of cytosolic calcium and protein tyrosine kinases

Abstract

We studied how the release of histamine and prostaglandin D 2 (PGD 2) were connected in stimulated rat peritoneal mast cells, and to what extent these processes were controlled by the cytosolic Ca 2+ concentration, [Ca 2+] i, and protein tyrosine kinases. In the presence of 1 mM CaCl 2, the G-protein activating compound 48/80 (10 μg/ml) evoked a transient rise in [Ca 2+] i and a relatively high secretion of histamine, but only a low release of PGD 2. In contrast, 5 μM thapsigargin (an inhibitor of endomembrane Ca 2+-ATPases) and 5 μM ionomycin evoked high and prolonged rises in [Ca 2+] i, and stimulated the cells to release relatively small amounts of histamine and high amounts of PGD 2. Stimulation of the cells with CaCl 2 and 10 μM ATP 4− gave only minor quantities of histamine and PGD 2, despite of the micromolar level of [Ca +] i reached. When CaCl 2 was replaced by EGTA, rises in [Ca 2+] i as well as release of histamine and PGD 2 were reduced with each agonist, but the preference of agonists to release more histamine or PGD 2 remained unchanged. In mast cells with depleted Ca 2+ stores, the addition of CaCl 2 stimulated the store-regulated Ca 2+ entry resulting in a prolonged rise in [Ca 2+] i. However, simultaneous addition of compound 48/80 and CaCl 2 was required for release of histamine and PGD 2. In cells with full stores, PGD 2 release evoked by compound 48/80 was greatly reduced by genistein and methyl-2,5-dihydroxycinnamate, two structurally unrelated inhibitors of protein tyrosine kinases, whereas histamine secretion was not influenced by these inhibitors. Similarly, with thapsigargin or ionomycin as agonist, PGD 2 release was more sensitive to the tyrosine kinase inhibitors than histamine secretion. We conclude that in activated rat peritoneal mast cells: (i) the influx of extracellular Ca 2+ potentiates agonist-evoked rises in [Ca 2+] i as well as histamine secretion and PGD 2 release; (ii) the amplitude of the [Ca 2+] i rise does not determine the preferential effect of agonists to release more histamine or more PGD 2; (iii) the relatively high PGD 2 release evoked by thapsigargin and ionomycin is probably due to their potency to evoke a prolonged rise in [Ca 2+] i and to activate protein tyrosine kinases.