Relationship between intracellular free calcium concentrations and the intracellular development of Toxoplasma gondii

J Histochem Cytochem. 1996 Oct;44(10):1123-9. doi: 10.1177/44.10.8813077.


We measured intracellular free calcium concentrations ([Ca++]i) in the subcellular compartments of Toxoplasma gondii infected living cells using microspectrofluorometry and Indo-1 staining. [Ca++]i mapping was defined in infected and uninfected cells and in the neoformed parasitophorous vacuole (PV) 24 and 48 hr after parasite inoculation. At 24 hr after infection, a [Ca++]i gradient (PV/cytoplasm) was observed in favor of the PV in 72% of infected cells (p<0.001). Inside of the PV (lumen and parasites), [Ca++]i values appeared to be homogeneously distributed. At 48 hr after infection, the parasites had replicated and formed typical rosettes of more than 16 parasites. At this step, a positive [Ca++]i gradient (PV/cytoplasm) was detected in all analyzed cells (p<0.001). This result suggests that the PV (lumen and parasites) represents an individual subcellular compartment within the host cell that includes an independent [Ca++]i. Moreover, after 48 hr the cytoplasmic [Ca++]i decreased significantly (39 nM) compared with that measured from uninfected cells (53 nM) (p <0.05). Furthermore, the exit of Toxoplasma mediated by the calcium ionophore 4BrA23187 was preceded by a rise of [Ca++]i to 1 mM in the PV. The [Ca++]i rise and the liberation of parasites from their host appear to be correlated. On the basis of these observations, we suggest that the increase of [Ca++]i in the vacuole may act as a signal that triggers the egress of T. gondii.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport / drug effects
  • Calcimycin / pharmacology
  • Calcium / analysis*
  • Calcium / physiology
  • Cell Compartmentation
  • Egtazic Acid / pharmacology
  • Fluorescent Dyes
  • Humans
  • Indoles
  • Intracellular Fluid / chemistry*
  • Ionophores / pharmacology
  • KB Cells / drug effects
  • KB Cells / parasitology*
  • Mice
  • Spectrometry, Fluorescence*
  • Toxoplasma / growth & development*
  • Vacuoles / chemistry
  • Vacuoles / parasitology


  • Fluorescent Dyes
  • Indoles
  • Ionophores
  • Calcimycin
  • Egtazic Acid
  • indo-1
  • Calcium