SPATIAL AND TEMPORAL MG2-CELLS( SIGNALING IN SINGLE HUMAN TRACHEAL GLAND)

The combined use of Mag-indo-1 probe and laser confocal UV-microspectr ofluorometry allowed us to investigate the spatial and temporal dynami c changes of the Mg2+ variations in human tracheal gland (HTG) cells a t the single cell level. Stimulation of HTG cells with either bradykin in, ouabain or extracellular high Mg2+ concentrations (up to 10 mM) in duced increases in intracellular Mg2+ concentration [Mg2+](i). From a cytosolic basal concentration of 0.8 +/- 0.3 mM in a medium free of Mg 2+, an increase in extracellular Mg2+ concentration from 1 to 10 mM, i ncreased cytosolic [Mg2+](i) from 1.4 +/- 0.6 to 1.8 +/- 0.8 mM after 10 min (p < 0.05). We also demonstrated using line-scanned spectral im ages within single cells, that the [Mg2+](i) is distributed uniformall y in the nucleoplasm, but in contrast, showed marked local differences among different cytoplasmic regions, thus suggesting a functional het erogeneity in the intracellular Mg2+ stores involved. The influx pathw ay for Mg2+ in HTG cells was not inhibited by verapamil and appeared t o be independent of [Ca2+](i). (C) 1996 Academic Press, Inc.