Na+/Ca2+ exchange in catfish retina horizontal cells: Regulation of intracellular Ca2+ store function

M. A. Micci, Burgess N. Christensen

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

The role of the Na+/Ca2+ exchanger in intracellular Ca2+ regulation was investigated in freshly dissociated catfish retinal horizontal cells (HC). Ca2+-permeable glutamate receptors and L-type Ca2+ channels as well as inositol 1,4,5-trisphosphate-sensitive and caffeine-sensitive intracellular Ca2+ stores regulate intracellular Ca2+ in these cells. We used the Ca2+-sensitive dye flue 3 to measure changes in intracellular Ca2+ concentration ([Ca2+]i) under conditions in which Na+/Ca2+ exchange was altered. In addition, the role of the Na+/Ca2+ exchanger in the refilling of the caffeine-sensitive Ca2+ store following caffeine- stimulated Ca2+ release was assessed. Brief applications of caffeine (1-10 s) produced rapid and transient changes in [Ca2+]i. Repeated applications of caffeine produced smaller Ca2+ transients until no further Ca2+ was released. Store refilling occurred within 1-2 min and required extracellular Ca2+. Ouabain-induced increases in intracellular Na+ concentration ([Na+](i)) increased both basal free [Ca2+](i) and caffeine-stimulated Ca2+ release. Reduction of external Na+ concentration ([Na+](o)) further and reversibly increased [Ca2+](i) in ouabain-treated HC. This effect was not abolished by the Ca2+ channel blocker nifedipine, suggesting that increases in [Na+](i) promote net extracellular Ca2+ influx through a Na+/Ca2+ exchanger. Moreover, when [Na+](o) was replaced by Li+, caffeine did not stimulate release of Ca2+ from the caffeine-sensitive store after Ca2+ depletion. The Na+/Ca2+ exchanger inhibitor 2',4'- dimethylbenzamil significantly reduced the caffeine-evoked Ca2+ response I and 2 min after store depletion.

Original languageEnglish (US)
Pages (from-to)C1625-C1633
JournalAmerican Journal of Physiology - Cell Physiology
Volume274
Issue number6 43-6
DOIs
StatePublished - Jun 1998

Keywords

  • Caffeine
  • Fluo 3
  • Retina
  • Ryanodine receptor

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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