Kinetics of calcium transport across the lymphocyte plasma membrane

M. Balasubramanyam, M. Kimura, Abraham Aviv, J. P. Gardner

Research output: Contribution to journalArticle

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Abstract

We have investigated plasma membrane Ca2+ transport by monitoring the fluorescence of human peripheral T-lymphocytes loaded with fura 2. Thapsigargin (TG) was utilized to block the Ca2+-ATPase of the endoplasmic reticulum and elevate the cytosolic Ca2+ (Ca(i)/2+). Ca2+ influx was inhibited by chelating extracellular Ca2+ with ethylene glycol-bis(β- aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). The rate of decline in the Ca(i)/2+ signal of TG-treated lymphocytes after exposure to EGTA was used to assess Ca2+ extrusion across the plasma membrane. Initial rates of Ca(i)/2+ decline were examined in cells suspended in Na+-containing and Na+-free solutions; initial rates were linearly related to the [Ca2+](i) at the onset of the Ca(i)/2+ decline and were unaffected by varying the extracellular Ca2+. Extracellular Na+ increased the rate of Ca2+ extrusion and decreased the threshold [Ca2+](i) for extrusion, indicating a substantial role for the Na+-Ca2+ exchange in Ca(i)/2+ homeostasis. Both decreased temperature and calmodulin inhibition significantly slowed the Ca(i)/2+ decline in Na+-free HEPES-buffered solution, suggesting Ca2+ extrusion under these conditions was mediated by the Ca2+ pump. Protein kinase C (PKC) activation or inhibition did not affect the Ca(i)/2+ decline parameters. However, Ca2+ accumulation and Mn2+ (a Ca2+ surrogate) uptake were significantly inhibited by activators of PKC. Cyclic nucleotides altered neither the parameters of the Ca(i)/2+ decline nor Mn2+ uptake. Thus human T-lymphocytes exhibit Na+- and Ca2+-dependent transporters characterized as the Na+-Ca2+ exchanger and Ca2+ pump. The main effect of PKC in these cells is the modulation of Ca2+ entry across the lymphocyte plasma membrane.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume265
Issue number2 34-2
StatePublished - Jan 1 1993

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Protein Kinase C
Thapsigargin
Egtazic Acid
Cell Membrane
Lymphocytes
Calcium
Sodium-Calcium Exchanger
HEPES
T-Lymphocytes
Ethylene Glycol
Fura-2
Cyclic Nucleotides
Calmodulin
Endoplasmic Reticulum
Ether
Adenosine Triphosphatases
Homeostasis
Fluorescence
Temperature
Acids

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cell Biology

Cite this

Balasubramanyam, M. ; Kimura, M. ; Aviv, Abraham ; Gardner, J. P. / Kinetics of calcium transport across the lymphocyte plasma membrane. In: American Journal of Physiology - Cell Physiology. 1993 ; Vol. 265, No. 2 34-2.
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Kinetics of calcium transport across the lymphocyte plasma membrane. / Balasubramanyam, M.; Kimura, M.; Aviv, Abraham; Gardner, J. P.

In: American Journal of Physiology - Cell Physiology, Vol. 265, No. 2 34-2, 01.01.1993.

Research output: Contribution to journalArticle

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