Nucleoplasmic Ca(2+)loading is regulated by mobilization of perinuclear Ca(2+)

Cell Calcium. 2000 Aug;28(2):127-36. doi: 10.1054/ceca.2000.0137.


Regulation of nucleoplasmic calcium (Ca(2+)) concentration may occur by the mobilization of perinuclear luminal Ca(2+)pools involving specific Ca(2+)pumps and channels of both inner and outer perinuclear membranes. To determine the role of perinuclear luminal Ca(2+), we examined freshly cultured 10 day-old embryonic chick ventricular cardiomyocytes. We obtained evidence suggesting the existence of the molecular machinery required for the bi-directional Ca(2+)fluxes using confocal imaging techniques. Embryonic cardiomyocytes were probed with antibodies specific for ryanodine-sensitive Ca(2+)channels (RyR2), sarco/endoplasmic reticulum Ca(2+)ATPase (SERCA2)-pumps, and fluorescent BODIPY derivatives of ryanodine and thapsigargin. Using immunocytochemistry techniques, confocal imaging showed the presence of RyR2 Ca(2+)channels and SERCA2-pumps highly localized to regions surrounding the nucleus, referable to the nuclear envelope. Results obtained from Fluo-3, AM loaded ionomycin-perforated embryonic cardiomyocytes demonstrated that gradual increases of extranuclear Ca(2+)from 100 to 1600 nM Ca(2+)was localized to the nucleus. SERCA2-pump inhibitors thapsigargin and cyclopiazonic acid showed a concentration-dependent inhibition of nuclear Ca(2+)loading. Furthermore, ryanodine demonstrated a biphasic concentration-dependence upon active nuclear Ca(2+)loading. The concomitant addition of thapsigargin or cyclopiazonic acid with ryanodine at inhibitory concentrations caused an significant increase in nuclear Ca(2+)loading at low concentrations of extranuclear added Ca(2+). Our results show that the perinuclear lumen in embryonic chick ventricular cardiomyocytes is capable of autonomously regulating nucleoplasmic Ca(2+)fluxes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium-Transporting ATPases / antagonists & inhibitors
  • Calcium-Transporting ATPases / metabolism
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism*
  • Cells, Cultured
  • Chick Embryo
  • Endoplasmic Reticulum / enzymology
  • Enzyme Inhibitors / pharmacology
  • Heart / embryology
  • Indoles / pharmacology
  • Intracellular Membranes / metabolism
  • Ionomycin / pharmacology
  • Ionophores / pharmacology
  • Myocardium / cytology
  • Myocardium / metabolism
  • Ryanodine / pharmacology
  • Ryanodine Receptor Calcium Release Channel / metabolism
  • Thapsigargin / pharmacology


  • Enzyme Inhibitors
  • Indoles
  • Ionophores
  • Ryanodine Receptor Calcium Release Channel
  • Ryanodine
  • Ionomycin
  • Thapsigargin
  • Calcium-Transporting ATPases
  • Calcium
  • cyclopiazonic acid