title: Estradiol-modified prolactin secretion independently of action potentials and Ca2+and blockade of outward potassium currents in GH3cells.
abstract: Estrogens facilitate prolactin (PRL) secretion acting on pituitary cells. In GH3cells, estradiol induces acute action potentials and oscillations of intracellular Ca2+associated with the secretagogue function. Estradiol modulates several ion channels which may affect the action potential rate and the release of PRL in lactotroph cells, which might depend on its concentration. The aims were to characterize the acute effect of supraphysiological concentrations of estradiol on Ca2+and noninactivating K+currents and measure the effect on the spontaneous action potentials and PRL release in the somatolactotroph cell line, GH3. Electrophysiological studies were carried out by voltage- and current-clamp techniques and ELISA determination of PRL secretion. Pharmacological concentrations of estradiol (above 1 μM), without a latency period, blocked Ca2+channels and noninactivating K+currents, including the large-conductance voltage- and Ca2+-activated K+channels (BK), studied in whole-cell nystatin perforated and in excided inside-out patches of GH3and CHO cells, transiently transfected with the human α-pore forming subunit of BK. The effect on BK was contrary to the agonist effect associated with the regulatory β1-subunits of the BK, which GH3cells lack, but its transient transfection did not modify the noninactivating current blockade, suggesting a different mechanism of regulation. Estradiol, at the same concentration range, acutely decreased the frequency of action potentials, an expected effect as consequence of the Ca2+channel blockade. Despite this, PRL secretion initially increased, followed by a decrease in long-term incubations. This suggests that, in GH3cells, supraphysiological concentrations of estradiol modulating PRL secretion are partially independent of extracellular Ca2+influx.
authors.affiliation: Farmacología, Departamento de Medicina, Universidad de Oviedo, Asturias, Spain. sanchezf@uniovi.es.|Farmacología, Facultad de Medicina y Ciencias de la Salud, Julián Clavería 6, 33006, Oviedo, Asturias, Spain. sanchezf@uniovi.es.|Instituto Universitario de Oncología del Principado de Asturias, Fundación Bancaria Caja de Ahorros de Asturias, Asturias, Spain. sanchezf@uniovi.es.
authors.forename: Manuel
authors.initials: M
authors.lastname: Sánchez
authors.affiliation: Instituto Universitario de Oncología del Principado de Asturias, Fundación Bancaria Caja de Ahorros de Asturias, Asturias, Spain.
authors.forename: Lorena
authors.initials: L
authors.lastname: Suárez
authors.affiliation: Farmacología, Departamento de Medicina, Universidad de Oviedo, Asturias, Spain.|Instituto Universitario de Oncología del Principado de Asturias, Fundación Bancaria Caja de Ahorros de Asturias, Asturias, Spain.
authors.forename: Begoña
authors.initials: B
authors.lastname: Cantabrana
authors.affiliation: Farmacología, Departamento de Medicina, Universidad de Oviedo, Asturias, Spain.|Instituto Universitario de Oncología del Principado de Asturias, Fundación Bancaria Caja de Ahorros de Asturias, Asturias, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Bordallo
mesh_terms: D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D016466:CHO Cells; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020013:Calcium Signaling / Q000187:drug effects*; D045744:Cell Line, Tumor; D003412:Cricetulus; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D004958:Estradiol / Q000494:pharmacology*; D052682:Lactotrophs / Q000187:drug effects* / Q000378:metabolism; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D013997:Time Factors; D014162:Transfection
chemical_list: D002121:Calcium Channel Blockers; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D026902:Potassium Channel Blockers; D004958:Estradiol; D011388:Prolactin
keywords: Adenohypophysis; Ca2+-channels; Estradiol; GH3 cells; Potassium channels; Prolactin; Voltage- and Ca2+-activated potassium channel