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Imaging of Ca 2 + Transients in Endothelial Cells of Single Perfused Capillaries: Correlation of Peak [Ca 2+ ] i with Sites of Macromolecule Leakage
Author(s) -
PAGAKIS S. N.,
CURRY F. E.
Publication year - 1994
Publication title -
microcirculation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.793
H-Index - 83
eISSN - 1549-8719
pISSN - 1073-9688
DOI - 10.3109/10739689409146749
Subject(s) - biophysics , permeability (electromagnetism) , ionomycin , calcium , chemistry , microvessel , extracellular , leakage (economics) , vascular permeability , endothelial stem cell , biology , biochemistry , in vitro , immunology , endocrinology , membrane , macroeconomics , economics , immunohistochemistry , organic chemistry
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 [Ca 2+ ] 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 [Ca 2+ ] i using a cooled CCD camera. Results: Control [Ca 2+ ] i was close to 60 nM in all regions. Control permeability was uniformly low in all microvessels. Exposure to ionomycin (5 mM) increased [Ca 2+ ] i in a biphasic manner, but not uniformly. There was variation in both time to peak (bimodal distribution) and peak [Ca 2+ ] 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 [Ca 2+ ] i about peak values. Extravascular leakage of fluorescently labeled albumin or low‐density lipoproteins was most prominent at sites where increases in [Ca 2+ ] i were largest. Conclusions: These data indicate that variation in [Ca 2+ ] 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.