title: Spontaneous Intracellular Calcium Oscillations and G(s) α Subunit Expression are Inversely Correlated with Secretory Granule Content in Pituitary Cells.
abstract: Cells of the pituitary tumour cell line GH(4) C(1) were exposed to epidermal growth factor, estradiol and insulin for 5 days, a treatment which resulted in 1) increased prolactin storage in secretory granules, 2) the loss of spontaneous [Ca(2+) ](1) oscillations, and 3) a selective reduction of the protein G(s) α, seen in immunoblots, cholera toxin labelling, and vasoactive intestinal peptide stimulation of adenylyl cyclase. In contrast, the glucocorticoid dexamethasone, which increases the expression of G(s) α, partially restored spontaneous [Ca(2+) ](1) oscillations and decreased prolactin storage. It is concluded that G(s) α levels in tumoral cells result in spontaneous electrical activity which may empty prolactin stores by the continuous activation of exocytosis.
authors.affiliation: Fondation pour Recherches Médicales, Department of Medicine, University of Geneva, 64 avenue de la Roseraie, CH-1211 Geneva, Switzerland Department of Pharmacology, University of Colorado Health Sciences Center, Campus Box C236, 4200 East Ninth Avenue, Denver, Colorado 80262, USA. Molecular Pathophysiology Branch, National Institute of Diabetes, Digestive and Kidney Diseases, NIH, Bethesda, Maryland 20892, USA.
authors.forename: C
authors.initials: C
authors.lastname: Chiavaroli
authors.forename: D M
authors.initials: DM
authors.lastname: Cooper
authors.forename: C L
authors.initials: CL
authors.lastname: Boyajian
authors.forename: R
authors.initials: R
authors.lastname: Murray-Whelan
authors.forename: N
authors.initials: N
authors.lastname: Demaurex
authors.forename: A M
authors.initials: AM
authors.lastname: Spiegel
authors.forename: W
authors.initials: W
authors.lastname: Schlegel