Mobilization of calcium by the brief application of oxytocin and prostaglandin E2 in single cultured human myometrial cells.
Intracellular calcium ([Ca2+]i) mobilization was studied in single cultured human myometrial cells in response to the agonists oxytocin and prostaglandin E2 (PGE2) using the fluorescent dye Fura-2. Oxytocin and PGE2 applications were associated with an increase in [Ca2+]i, although there was a marked intercell variation in the amplitude of the agonist-induced response. Removal of extracellular calcium ([Ca2+]o) reduced the oxytocin-induced rise and abolished the PGE2-induced rise in [Ca2+]i, thereby demonstrating that oxytocin but not PGE2 can mobilize intracellular stores of calcium. In nominally calcium-free medium, [Ca2+]i was not increased by PGE2 but subsequent application of oxytocin increased [Ca2+]i, thereby demonstrating that, within a single cell, calcium stores were mobilized by oxytocin and not PGE2. The intracellular calcium stores were completely depleted by a single application of oxytocin and not replenished in the absence of [Ca2+]o. Perfusion with calcium-containing medium for 100 s enabled store refilling. Cell depolarization by 140 mM-K+ caused a transient increase followed by a sustained elevation of [Ca2+]i on which were superimposed small fluctuations. Oxytocin caused an influx of calcium in cells depolarized by K+. This was more marked than that obtained with PGE2.
Thornton
S
S
Department of Obstetrics and Gynaecology, Princess Mary Maternity Hospital, Newcastle upon Tyne.
Gillespie
J I
JI
Greenwell
J R
JR
Dunlop
W
W
D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003470:Culture Media; D015232:Dinoprostone / Q000494:pharmacology; D005260:Female; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D008564:Membrane Potentials; D009215:Myometrium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010121:Oxytocin / Q000494:pharmacology; D014590:Uterine Contraction / Q000187:drug effects / Q000502:physiology
D003470:Culture Media; D010121:Oxytocin; D015232:Dinoprostone; D002118:Calcium