Oxytocin-induced oscillations of cytoplasmic Ca2+ in human myometrial cells.

Background. To investigate the mechanisms of oxytocin (OT) induced oscillations of the cytoplasmic Ca 2+ concentration ([Ca 2+ ] i ) in cultured human myometrial cells. Methods. [Ca 2+ ] i was measured in individual myometrial cells by dual wavelength spectrophotofluorometry using the fluorescent indicator fura-2. Myometrium was obtained at abdominal hysterectomy ( n =8) and during cesarean section ( n =7). Results. OT (10-300 nM) typically induced [Ca 2+ ] i oscillations with frequencies in the 0.6-0.8/min range. There were no obvious differences in the responses of cells taken from non-pregnant and term pregnant women. The frequency and amplitude of the oscillations were not significantly affected by OT concentrations up to 300 nM. The amplitude of the oscillations decreased in the presence of the voltage-dependent Ca 2+ channel antagonist verapamil and gradually disappeared in Ca 2+ -free medium. The oscillations were further blocked by the inorganic Ca 2+ antagonist La 3+ and by the intracellular Ca 2...