Eosinophil chemotactic factor released from murine bone marrow derived cultured mast cells

Release of eosinophil chemotactic factor (ECF) from murine bone marrow derived cultured mast cells was examined. As the indicator cells for in vitro chemotaxis assay, eosinophils were obtained from bone marrow of cyclophosphamide-treated and Toxocara canis-infected mice. When cultured mast cells were stimulated with calcium ionophore A23187 or IgE-antigen, they released ECF as well as beta-hexosaminidase. ECF-release was not observed when they were stimulated with compound 48/80. Freeze-thawed extract of cultured mast cells contained beta-hexosaminidase but no ECF activity, showing that the ECF is newly synthesized after stimulation. ECF was even spontaneously released when cultured mast cells were incubated for more than 30 min at 37 degrees C. The ECF released from cultured mast cells was low molecular weight substance (less than 1300 Dalton), and was resistant to digestion with carboxypeptidase. The ECF was extractable into chloroform-methanol (2:1) at acidic pH. Judging from these physicochemical characteristics, ECF released from cultured mast cells may be an arachidonic acid metabolite.