ADRENOCORTICOTROPIN INDUCES CALCIUM OSCILLATIONS IN ADRENAL FASCICULATA CELLS - SINGLE-CELL IMAGING

With fluorescence microscopic imaging, we have demonstrated that the C a2+ signaling occurred in individual Calcium Green-1 loaded bovine adr enal fasciculata cells upon stimulation with adrenocorticotropin (ACTH ) at physiological concentration of 0.1-100 pM. We observed three patt erns of Ca2+ signaling which were Ca2+ oscillations (33%), step-like i ncrease in Ca2+ concentration (10%), and Ca2+ oscillations superimpose d on step-like increase in Ca2+ (57%). The oscillation in intracellula r Ca2+ concentration occurred with a frequency around 0.04 Hz. When Ca 2+ signaling upon ACTH stimulation was inhibited by the treatment with EGTA, the corticoid production was considerably suppressed. The resul ts suggest that the Ca2+ signaling is a probable candidate of the seco nd messenger for ACTH-induced steroid hormone synthesis in zona fascic ulata cells. (C) 1996 Academic Press, Inc.