Correlation between electrical activity and intracellular Ca2+ oscillations in GH3 rat anterior pituitary cells

Cell Calcium. 2002 Feb;31(2):65-78. doi: 10.1054/ceca.2001.0260.

Abstract

Simultaneous measurements of electrical activity and intracellular Ca(2+) levels were performed in perforated-patch current-clamped individual GH3 cells. Both in cells showing brief (<100 ms) and long action potentials (APs), we found a good correlation between the averaged intracellular Ca2+ concentration ([Ca2+]i) and AP frequency, but not between the mean [Ca2+]i and AP duration. Nevertheless, the magnitude of spontaneous Ca2+ oscillations was highly dependent on the size and duration of the APs. The decay of the Ca2+ transients was not slowed when the size of the oscillations was varied either spontaneously or after elongation of the AP with the K+ channel blocker tetraethyl ammonium. Furthermore, the recovery from Ca2+ loads similar to those induced by the APs was slightly retarded after treatment of the cells with intracellular store Ca2+-ATPase inhibitors. Among previous results showing that caffeine-induced [Ca2+]i increases are secondary to electrical activity enhancements in GH3 cells, these data indicate that the Ca2+ entry triggered via APs is the primary determinant of the [Ca2+]i variations, and that Ca2+-induced Ca2+ release has a minor contribution to Ca2+ oscillations recorded during spontaneous activity. They also point to modulation of electrical activity patterns as a crucial factor regulating spontaneous [Ca2+]i signalling, and hence pituitary cell functions in response to physiological secretagogues.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials
  • Animals
  • Calcium / metabolism*
  • Calcium Signaling
  • Cell Line
  • Hydroquinones / pharmacology
  • Patch-Clamp Techniques
  • Pituitary Gland, Anterior / cytology
  • Pituitary Gland, Anterior / metabolism*
  • Rats
  • Thyrotropin-Releasing Hormone / physiology

Substances

  • Hydroquinones
  • 2,5-di-tert-butylhydroquinone
  • Thyrotropin-Releasing Hormone
  • Calcium