These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Roles of intracellular and extracellular calcium in the kinetic profile of adrenocorticotropin secretion by perifused rat anterior pituitary cells. I. Corticotropin-releasing factor stimulation.
    Author: Won JG, Orth DN.
    Journal: Endocrinology; 1990 Feb; 126(2):849-57. PubMed ID: 2153529.
    Abstract:
    We examined the effects of removing extracellular Ca2+ (Ca2+e), depleting intracellular Ca2+ (Ca2+i), inhibiting Ca2(+)-dependent calmodulin, blocking voltage-sensitive Ca2+ channels, and combining Ca2+i depletion with exposure to glucocorticoid on the secretion of ACTH by perifused dispersed rat anterior pituitary cells stimulated with ovine CRF and 8-bromo-cAMP (8-Br-cAMP). A time-course analysis of the effect of perifusing the cells for 60 min with Ca2(+)-free medium on 10 nM CRF-stimulated ACTH release revealed that inhibition required about 3 min to begin and about 40 min to reach maximal effect. Within 2 min of restoring Ca2+ to the medium, ACTH secretion rebounded for about 5 min before falling to the pre-Ca2+e removal rate. A similar pattern and time course were observed when Ca2+e was more completely removed by perifusing the cells with Ca2(+)-free medium containing 2 mM EGTA, except that greater suppression was observed. Removing Ca2+e reduced CRF- and 5 mM 8-Br-cAMP-induced ACTH release by 54% and 49%, respectively, and delayed by 1 min the response to 8-Br-cAMP, but not that to CRF. Perifusing 0.2 mM nimodipine, a dihydropyridine Ca2+ channel blocker, before and after restoration of Ca2+ to the Ca2(+)-free medium inhibited ACTH release by 40-48%, and the blockade persisted for at least 70 min after nimodipine was removed from the medium. When intracellular Ca2+ was depleted by perifusing the cells with Ca2(+)-free/EGTA medium containing the Ca2+ ionophore A23187 to facilitate the efflux of Ca2+i, CRF- and 8-Br-cAMP-stimulated ACTH release were reduced by 70% and 71%, respectively, and the responses to both agents were delayed by 1 min. Preperifusion of the cells with 5 microM penfluridol, a calmodulin inhibitor, reduced CRF- and 8-Br-cAMP-induced ACTH release by 54% and 41%, respectively. The combination of Ca2+i depletion and perifusion with 100 nM dexamethasone, a maximally inhibitory concentration, inhibited CRF- and 8-Br-cAMP-stimulated ACTH release by 82% and 83%, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
    [Abstract] [Full Text] [Related] [New Search]