Depolarization-evoked Ca2+ release in a non-excitable cell, the rat megakaryocyte

J Physiol. 1999 Mar 1;515 ( Pt 2)(Pt 2):385-90. doi: 10.1111/j.1469-7793.1999.385ac.x.

Abstract

1. The effect of membrane potential on [Ca2+]i in rat megakaryocytes was studied using simultaneous whole-cell patch clamp and fura-2 fluorescence recordings. 2. Depolarization from -75 to 0 mV had no effect on [Ca2+]i in unstimulated cells, but evoked one or more spikes of Ca2+ increase (peak increase: 714 +/- 95 nM) during activation of metabotropic purinoceptors by 1 microM ADP. 3. The depolarization-evoked Ca2+ increase was present in Ca2+-free medium and also following removal of Na+. Thus depolarization mobilizes Ca2+ from an intracellular store without a requirement for altered Na+-Ca2+ exchange activity. 4. Intracellular dialysis with heparin blocked the depolarization-evoked Ca2+ increase, indicating a role for functional IP3 receptors. 5. Under current clamp, ADP caused the membrane potential to fluctuate between -43 +/- 1 and -76 +/- 1 mV. Under voltage clamp, depolarization from -75 to -45 mV evoked a transient [Ca2+]i increase (398 +/- 91 nM) during exposure to ADP. 6. We conclude that during stimulation of metabotropic purinoceptors, membrane depolarization over the physiological range can stimulate Ca2+ release from intracellular stores in the rat megakaryocyte, a non-excitable cell type. This may represent an important mechanism by which electrogenic influences can control patterns of [Ca2+]i increase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Diphosphate / pharmacology
  • Animals
  • Calcium / metabolism*
  • Electrophysiology
  • Heparin / pharmacology
  • Intracellular Membranes / metabolism
  • Male
  • Megakaryocytes / metabolism
  • Megakaryocytes / physiology*
  • Membrane Potentials / drug effects
  • Osmolar Concentration
  • Patch-Clamp Techniques
  • Rats
  • Rats, Wistar
  • Receptors, Purinergic / drug effects
  • Receptors, Purinergic / metabolism
  • Sodium / pharmacology

Substances

  • Receptors, Purinergic
  • Adenosine Diphosphate
  • Heparin
  • Sodium
  • Calcium