Two separate plasma membrane Ca2+ carriers participate in receptor-mediated Ca2+ influx in rat hepatocytes

George E.N. Kass, Sek C. Chow, Annie Gahm, Dominic Luc Webb, Per Olof Berggren, Juan Llopis, Sten Orrenius

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

The plasma membrane Ca2+ carrier system involved in receptor-mediated Ca2+ entry was studied. Using the Ca2+ readdition protocol, the rate of cytosolic free Ca2+ concentration ([Ca2+]i) increase in vasopressin-pretreated hepatocytes was significantly higher than in thapsigargin- or 2,5-di(tert-butyl)hydroquinone-pretreated cells. The addition of Mn2+ to unstimulated hepatocytes resulted in a biphasic quench of fura-2 fluorescence. After an initial phase that was fast in rate but of short duration, the rate of fura-2 quench by Mn2+ became much slower and lasted until all the cellular fura-2 was quenched. Pretreatment of the cells with vasopressin only accelerated the rate of the latter phase but not of the initial one. In agonist-stimulated cells, acidification of the extracellular medium or the presence of ruthenium red, econazole or SK&F 96365 decreased the rates of both [Ca2+]i increase and Mn2+ entry upon addition of the respective cation. By contrast, neomycin and N-tosyl-l-phenylalanine chloromethyl ketone markedly decreased the rate of [Ca2+]i increase upon Ca2+ readdition but had no effect on vasopressin-stimulated Mn2+ entry. None of the treatments affected the ability of vasopressin and thapsigargin to mobilize the internal Ca2+ store. It is concluded that in hepatocytes the two pathways of receptor-mediated Ca2+ entry control two distinct yet pharmacologically related cation carriers.

Original languageEnglish (US)
Pages (from-to)226-233
Number of pages8
JournalBBA - Molecular Cell Research
Volume1223
Issue number2
DOIs
StatePublished - Sep 8 1994

Keywords

  • 2,5-Di(tert-butyl)hydroquinone
  • Calcium entry
  • Hepatocyte
  • Inositol phosphate
  • Signalling
  • Thapsigargin

ASJC Scopus subject areas

  • Biophysics
  • Cell Biology
  • Molecular Biology

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    Kass, G. E. N., Chow, S. C., Gahm, A., Webb, D. L., Berggren, P. O., Llopis, J., & Orrenius, S. (1994). Two separate plasma membrane Ca2+ carriers participate in receptor-mediated Ca2+ influx in rat hepatocytes. BBA - Molecular Cell Research, 1223(2), 226-233. https://doi.org/10.1016/0167-4889(94)90230-5