Biphasic elevation of [Ca(2+)](i) in individual human spermatozoa exposed to progesterone

J. C. Kirkman-Brown, C. Bray, P. M. Stewart, C. L. R. Barratt, S. J. Publicover

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70 Citations (Scopus)

Abstract

Fluorimetric studies on progesterone-induced [Ca(2+)](i) signalling in mammalian spermatozoa show both the well-characterised [Ca(2+)](i) transient and a subsequent sustained phase. However, the sustained phase is thought to reflect release of the fluorochrome during the acrosome reaction and has not been subject to critical investigation. We have used single-cell imaging of [Ca(2+)](i) to analyse the progesterone-induced [Ca(2+)](i) response in large numbers (>2000) of capacitated, human spermatozoa. In 70% of cells, treatment with progesterone induced a transient increase, which typically peaked within 1 min and decayed with a similar time course. Upon rapid application of progesterone this response peaked within 5-20 s. In 35% of progesterone-treated spermatozoa a sustained elevation of [Ca(2+)](i) occurred, which became discernible during the falling phase of the transient response and persisted for at least 20 min. Both [Ca(2+)](i) responses were localised to the postacrosomal region. Averaging of large numbers of single cell responses generated traces similar to those seen in fluorimetric studies. Although the sustained response was strongly associated with the initial, transient response, a few spermatozoa generated sustained responses that were not preceded by a significant transient response (5% of cells). It is concluded that a genuine biphasic [Ca(2+)](i) signal is activated by progesterone and that the sustained response is a discrete signalling event with biological significance.

Original languageEnglish
Pages (from-to)326-35
Number of pages10
JournalDevelopmental Biology
Volume222
Issue number2
DOIs
Publication statusPublished - 15 Jun 2000

Keywords

  • Acrosome Reaction/drug effects
  • Activity Cycles
  • Calcium/metabolism
  • Calcium Signaling/drug effects
  • Humans
  • Kinetics
  • Male
  • Microscopy, Confocal
  • Progesterone/pharmacology
  • Reproducibility of Results
  • Sperm Capacitation/drug effects
  • Spermatozoa/cytology
  • Time Factors

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