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

Microcirculation. 1994 Dec;1(4):213-30. doi: 10.3109/10739689409146749.

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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Capillary Permeability
  • Endothelium, Vascular / metabolism
  • Endothelium, Vascular / ultrastructure*
  • Fluorescent Dyes
  • Fura-2
  • Image Processing, Computer-Assisted
  • Male
  • Microscopy, Fluorescence
  • Microscopy, Video
  • Rana pipiens
  • Time Factors

Substances

  • Fluorescent Dyes
  • Calcium
  • Fura-2