TY - JOUR
T1 - Cytosolic free calcium levels in cultured pituitary cells separated by centrifugal elutriation
T2 - Effect of gonadotropin-releasing hormone
AU - Limor, Rona
AU - Ayalon, Dan
AU - Capponi, Alessandro M.
AU - Childs, Gwen V.
AU - Naor, Zvi
PY - 1987/2
Y1 - 1987/2
N2 - The cytosolic concentration of free Ca2+ ([Ca2+]i) in normal rat pituitary cells separated by centrifugal elutriation was monitored with the fluorescent Ca2+ indicator Quin 2. GnRH (10-7 M) induced a rapid rise (6–8 sec) in the gonadotroph's [Ca2+]i, followed by a plateau phase of prolonged elevated [Ca2+]i which lasted about 15 min. The stimulatory effect of GnRH was dose dependent, with an ED50 of 10-9 M, and was blocked by the potent antagonist [Dp-Glu1.pclPhe2.DTrp3,6]GnRH. GnRH elevated [Ca2+]iOnly in gonadotroph- enriched cell fractions, whereas TRH and GH-releasing factor (GRF) elevated [Ca2+]i in mammotroph- and somatotroph- enriched cells fractions, respectively. A rapid increase (first phase) in [Ca2+]i induced by GnRH was observed in Ca2+-free medium containing EGTA, but this rapid phase was terminated within 2 min. Readdition of Ca2+ to the medium induced a second slower rise in [Ca2+]i (plateau phase). Addition of K+ caused a rapid rise in [Ca2+]i, which was dependent on extracellular Ca2+, but was not affected by prior stimulation with GnRH. On the other hand, stimulation of gonadotroph's [Ca2+]i response by GnRH desensitized the cells to a subsequent GnRH challenge within the time frame studied. These findings indicate an elevation of [Ca2+]i induced by GnRH, TRH, and GRF in their respective separated target cells in the rat pituitary. The rise in [Ca2+]i in GnRH-stimulated gonadotrophs originates partly from intracellular Ca2+ pools and partly from influx of Ca2+ across the cell membrane.
AB - The cytosolic concentration of free Ca2+ ([Ca2+]i) in normal rat pituitary cells separated by centrifugal elutriation was monitored with the fluorescent Ca2+ indicator Quin 2. GnRH (10-7 M) induced a rapid rise (6–8 sec) in the gonadotroph's [Ca2+]i, followed by a plateau phase of prolonged elevated [Ca2+]i which lasted about 15 min. The stimulatory effect of GnRH was dose dependent, with an ED50 of 10-9 M, and was blocked by the potent antagonist [Dp-Glu1.pclPhe2.DTrp3,6]GnRH. GnRH elevated [Ca2+]iOnly in gonadotroph- enriched cell fractions, whereas TRH and GH-releasing factor (GRF) elevated [Ca2+]i in mammotroph- and somatotroph- enriched cells fractions, respectively. A rapid increase (first phase) in [Ca2+]i induced by GnRH was observed in Ca2+-free medium containing EGTA, but this rapid phase was terminated within 2 min. Readdition of Ca2+ to the medium induced a second slower rise in [Ca2+]i (plateau phase). Addition of K+ caused a rapid rise in [Ca2+]i, which was dependent on extracellular Ca2+, but was not affected by prior stimulation with GnRH. On the other hand, stimulation of gonadotroph's [Ca2+]i response by GnRH desensitized the cells to a subsequent GnRH challenge within the time frame studied. These findings indicate an elevation of [Ca2+]i induced by GnRH, TRH, and GRF in their respective separated target cells in the rat pituitary. The rise in [Ca2+]i in GnRH-stimulated gonadotrophs originates partly from intracellular Ca2+ pools and partly from influx of Ca2+ across the cell membrane.
UR - http://www.scopus.com/inward/record.url?scp=0023106758&partnerID=8YFLogxK
U2 - 10.1210/endo-120-2-497
DO - 10.1210/endo-120-2-497
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AN - SCOPUS:0023106758
SN - 0013-7227
VL - 120
SP - 497
EP - 503
JO - Endocrinology
JF - Endocrinology
IS - 2
ER -