Imaging of Ca2+ transients in endothelial cells of single perfused capillaries: correlation of peak [Ca2+]i with sites of macromolecule leakage.

S. N. Pagakis, F. E. Curry

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Abstract

OBJECTIVE: To investigate the mechanisms responsible for variation in the macromolecular leakage (formation of localized leaky sites) in venular microvessels with increased permeability, we examined the hypothesis that cytoplasmic calcium concentration [Ca2+]i, does not increase uniformly within microvessel endothelial cells. METHODS: We loaded the endothelial cells forming the walls of venular microvessels in frog mesentery with fura-2, and imaged [Ca2+]i using a cooled CCD camera. RESULTS: Control [Ca2+]i was close to 60 nM in all regions. Control permeability was uniformly low in all microvessels. Exposure to ionomycin (5 mM) increased [Ca2+]i in a biphasic manner, but not uniformly. There was variation in both time to peak (bimodal distribution) and peak [Ca2+]i (274 +/- 13 nM; mean variation above or below the peak value was 110 nM). Raising extracellular calcium from 1.1 to 5 mM increased the mean variation of [Ca2+]i about peak values. Extravascular leakage of fluorescently labeled albumin or low-density lipoproteins was most prominent at sites where increase in [Ca2+]i were largest. CONCLUSIONS: These data indicate that variation in [Ca2+]i within individual endothelial cells or groups of cells could account, at least in part, for the distribution of localized leakage sites for macromolecules in venular microvessels in the high-permeability state.

Original languageEnglish (US)
Pages (from-to)213-230
Number of pages18
JournalMicrocirculation (New York, N.Y. : 1994)
Volume1
Issue number4
StatePublished - Dec 1994

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ASJC Scopus subject areas

  • Physiology
  • Genetics
  • Cardiology and Cardiovascular Medicine

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