Na+/Ca2+ exchange-mediated calcium entry in human lymphocytes

M. Balasubramanyam, C. Rohowsky-Kochan, J. P. Reeves, J. P. Gardner

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Regulation of cytosolic Ca2+ and cytosolic Na+ is critical for lymphocyte cation homeostasis and function. To examine the influence of cytosolic Na+ on Ca2+ regulation in human peripheral blood lymphocytes, Ca2+ entry and cytosolic Ca2+ (measured with fura-2) were monitored in cells in which cytosolic Na+ was increased and/or the Na+ gradient was decreased by reduction of external Na+ concentration. Ouabain-treated cells (0.1 mM for 30 min at 37°C), suspended in Na+-free medium, showed a 30-65% increase in Ca2+ uptake compared to cells in 140 mM Na+ medium. Enhanced Ca2+ influx was entirely dependent on ouabain pretreatment and reversal of the Na+ gradient. Na pump inhibition or Na ionophore addition and subsequent exposure to Na+-free medium resulted in a sustained elevation of cytosolic Ca2+. As preincubation of cells in Ca2+-free medium further enhanced the ouabain-dependent increase in cytosolic Ca2+, the effects of the microsomal Ca2+-ATPase inhibitor thapsigargin on Ca2+ influx and cytosolic Ca2+ were studied. Thapsigargin stimulated Ca2+ entry following ouabain pretreatment and reversal of the Na+ gradient; the effects of thapsigargin were retained in the presence of LaCl3, a potent inhibitor of store- dependent calcium influx pathways. These results show lymphocytes demonstrate Na+/Ca2+ exchange activity and suggest the Na+/Ca2+ exchanger modulates cytosolic Ca2+ following intracellular Ca2+ store depletion.

Original languageEnglish (US)
Pages (from-to)2002-2008
Number of pages7
JournalJournal of Clinical Investigation
Issue number5
StatePublished - 1994

All Science Journal Classification (ASJC) codes

  • Medicine(all)


  • Ca uptake
  • human T lymphocytes
  • intracellular Ca stores
  • store-dependent Ca influx
  • thapsigargin


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