title: Mechanism of histamine release by alpha-chymotrypsin from isolated rat mast cells.
abstract: Alpha-chymotrypsin (CT) was modified chemically and physically by the treatments with diisopropyl fluorophosphate, L-(1-tosylamide-2-phenyl) ethylchloromethylketone, hydrogen peroxide and heat. After these treatments, CT lost or decreased both the enzymic activity and ability of releasing histamine from rat mast cells. Ca++ was essential for histamine release by CT, while it enhanced only slightly the enzymic activity. Process of histamine release by CT could be separated into two stages: CT-dependent but not Ca++-dependent, and Ca++-dependent but not CT-dependent. The activated state of mast cells produced by CT decayed rapidly at 37 degrees C in the absence of Ca++, but these cells responded to Ca++ by adding CT once again, suggesting reconstitution of cell membrane structure affected by CT. Isoproterenol, epinephrine, prostaglandin E1, and dibutyryl-cyclic AMP (0.01-0.1 mM) did not inhibit release of histamine induced by CT. Neither theophylline (0.01-0.1 mM) alone nor the combinations of these cyclic AMP-active agents with theophylline inhibited the release of histamine. But, in the presence of papaverine (0.01-0.1 mM) a marked, dose-dependent inhibition was observed. These data suggest that 1) release of histamine by CT from rat mast cells is causally related to its hydrolytic activity, 2) this activity causes a reversible change on mast cell membrane which probably facilitates Ca++-influx through the cell membrane, and 3) there are subtle differences among CT, compound 48/80 and antigens concerning the effect of cyclic AMP-active agents in histamine-releasing mechanisms in mast cells.
mesh_terms: D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology; D002918:Chymotrypsin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D006636:Histamine Release / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D007531:Isoflurophate; D007545:Isoproterenol / Q000494:pharmacology; D008407:Mast Cells / Q000378:metabolism*; D010208:Papaverine / Q000494:pharmacology; D011458:Prostaglandins E / Q000494:pharmacology; D011489:Protein Denaturation; D051381:Rats; D013696:Temperature; D013806:Theophylline / Q000494:pharmacology; D014108:Tosylphenylalanyl Chloromethyl Ketone
chemical_list: D002413:Cations, Divalent; D011458:Prostaglandins E; D007531:Isoflurophate; D014108:Tosylphenylalanyl Chloromethyl Ketone; D003994:Bucladesine; D013806:Theophylline; D010208:Papaverine; D000242:Cyclic AMP; D002918:Chymotrypsin; D007545:Isoproterenol; D002118:Calcium; D004837:Epinephrine