[Ca2+](i) signaling in pregnant human myometrium

S. E. Szal, John Repke, E. W. Seely, S. W. Graves, C. A. Parker, K. G. Morgan

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Abstract

The purpose of the present study was to determine the changes in intracellular ionized calcium concentration ([Ca2+](i)) or [Ca2+](i) sensitivity accompanying spontaneous and agonist-induced contraction of human myometrium at term pregnancy, as well as to quantify the response to three prototypical agonists: 1) oxytocin, 2) vasopressin, and 3) phenylephrine. Uterine biopsies were obtained at the time of cesarean section from patients who delivered at or near full-term gestation. These preparations were used to measure isometric force development and [Ca2+](i) levels with the luminescent calcium indicator aequorin. Concentration-response relationships were determined with respect to isometric force development in the presence of the agonist. [Ca2+](i)-force relationships were determined with respect to spontaneous phasic contractions, as well as agonist-induced phasic and tonic contractions. The results provide evidence that the phasic nature of term human myometrium is due to 1) the resting [Ca2+](i) level being less than the calcium threshold for contractions and 2) the inability of the tissue to maintain high [Ca2+](i) levels for prolonged periods of time. In addition, calcium-independent mechanisms of regulation were suggested by the relatively minor calcium sensitizing action of oxytocin and the observation that relaxation of tonic contractions preceded the fall in [Ca2+](i) levels.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume267
Issue number1 30-1
Publication statusPublished - Jan 1 1994

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All Science Journal Classification (ASJC) codes

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

Cite this

Szal, S. E., Repke, J., Seely, E. W., Graves, S. W., Parker, C. A., & Morgan, K. G. (1994). [Ca2+](i) signaling in pregnant human myometrium. American Journal of Physiology - Endocrinology and Metabolism, 267(1 30-1).