We studied membrane potential changes accompanying Ca2+ signals in two different cellular models, human lymphocytes and rat mast cells. The cells were stimulated with agents known to induce both Ca2+ release from internal stores and influx of extracellular Ca2+, namely thapsigargin and ionomycin for lymphocytes and compound 48/80 for mast cells. The fluorescent dye bis-oxonol was used to determine the membrane potential and Fura-2 to monitor Ca2+ concentration. Thapsigargin induced a hyperpolarization in lymphocytes, temporally correlated with the increase in intracellular Ca2+ concentration. This hyperpolarizalion is due to the activation of a K+ conductance and it has two phases: a first phase independent on external Ca2+ and a second one blocked in a Ca2+ free medium. High doses of ionomycin induce a Ca+2-dependent depolarization attributed to a massive influx of external Ca+2. Stimulation of mast cells with compound 48/80 induces a fast hyperpolarization as well as a big increase in intracellular Ca2+ level. Besides different time courses, this hyperpolarization differs from that induced by thapsigargin in lymphocytes in other two aspects: it is carried mainly by a Cl- current and it is completely inhibited in the absence of extracellular Ca2+.
|Original language||English (US)|
|State||Published - 1997|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology