ASYNCHRONOUS DYNAMIC CHANGES OF INTRACELLULAR FREE CA2-CELLS INDUCED BY NEUTROPHIL ELASTASE( AND POSSIBLE EXOCYTOSIS IN HUMAN TRACHEAL GLAND)

Measurements of the intracellular free calcium concentration [Ca2+](i) in single cells of the human tracheal gland cell line MM 39 demonstra te dynamic changes in [Ca2+](i) after their exposure to human neutroph il elastase (HNE). A heterogeneity in [Ca2+](i) responses measured cel l to cell in monolayer culture is evident : cells generate an initial [Ca2+](i) peak rise with or without a delayed time (up to 180 sec) fol lowed either by a rapid return to baseline, asynchronous oscillations or a sustained plateau phase. From basal concentration of 85+/- 15 nM, HNE (1 mu M) produces a [Ca2+](i) increase of 91 +/- 66 nM in about 5 0 % of responding cells. At lower concentrations of HNE (0.1 mu M, 0.0 1 mu M), the [Ca2+](i) rise remains similar, but only 30-40 % of the c ells are responding. Pretreatment of cells with the recombinant elafin protein, a specific elastase inhibitor, reduces both the [Ca2+](i) re sponse to HNE and the number of responding cells. Electron microscopy observations reveal an increased number of secretory granules located beneath the cell plasma membrane after HNE treatment. These results su ggest that intracellular [Ca2+](i) changes may be associated to the HN E-induced exocytosis in human tracheal gland cells. These findings cou ld have implications with regard to the pathogenesis of increased mucu s secretion in human airway diseases. (C) 1995 Academic Press, Inc.