Intracellular calcium buffering shapes calcium oscillations in Xenopus melanotropes

W. Koopman, W. Scheenen, L. Schoolderman, P. Cruijsen, E. Roubos, B. Jenks

Research output: Contribution to journalArticleAcademicpeer-review

7 Citations (Scopus)

Abstract

The pituitary melanotrope cell of Xenopus laevis displays cytosolic Ca2+ oscillations that arise for the interplay between the burst-like openings of voltage-operated Ca2+ channels and Ca2+-extrusion mechanisms. We have previously shown that Ca2+-extrusion rates increase with increases in [Ca2+]i, suggesting that Ca2+ itself plays a role in shaping the Ca2+ oscillations. The purpose of the present study was to test this hypothesis by manipulating the intracellular Ca2+ buffering capacity of the cell and determining the consequences of such manipulations for the shape of the Ca2+ oscillations. We manipulated the cytosolic buffering capacity by loading the fast Ca2+ chelator BAPTA into cells. During loading the [Ca2+]i was dynamically imaged with confocal laser scanning microscopy. The basal [Ca2+]i was reduced with BAPTA loading and this reduction was associated with lower Ca2+-extrusion rates, a broadening of the Ca2+ oscillations and declined oscillation frequencies. Short loading periods of the buffer led to new, stable patterns of Ca2+ signaling and to reduced but stable levels of peptide secretion. We propose that the cytosolic Ca2+ buffer capacity, and thus by inference the profile of intracellular Ca2+ buffering proteins, is an important factor in setting the frequency and shape of Ca2+ oscillations.

Original languageEnglish
Pages (from-to)250-256
Number of pages7
JournalPflugers Archiv European Journal of Physiology
Volume443
Issue number2
DOIs
Publication statusPublished - 2001
Externally publishedYes

Keywords

  • α-melanocyte stimulating hormone
  • Ca buffering
  • Ca oscillations
  • Melanotrope
  • Secretion
  • Xenopus laevis

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