Endothelial gaps and permeability of venules in XXXX tracheas exposed to inflammatory stimuli.

@entity825 @entity575 @entity7292 @entity35 @entity13624
This study determined the number of endothelial gaps in venules of the @entity35 @entity825 and related these values to the amount of plasma extravasation after an inflammatory stimulus ( @entity13624 ). From 1 to 30 min after the stimulus, vessels were fixed by vascular perfusion, and endothelial cell borders were stained with @entity7292 , which made it possible to quantify the number and distribution of endothelial gaps. It also was possible to quantify the leukocyte attachment sites, to measure the size, shape, and number of endothelial cells, and to delineate the architecture of the tracheal vasculature. Sites of increased vascular permeability were localized with Monastral blue B, india ink, or fluorescent microspheres. After the stimulus, the @entity575 lines around endothelial cells of postcapillary venules and collecting venules were interrupted by stereotyped @entity575 dots (diam, 1.4 +/- 0.03 microns; +/- SE), which were found by electron microscopy to be @entity575 deposits at endothelial gaps. The dots were most abundant in the smallest postcapillary venules (diam, 7-20 microns) where Monastral blue extravasation was greatest. The number of @entity575 dots (14.4 +/- 0.7 dots/endothelial cell) and the amount of extravasation were maximal 1 min after the stimulus. However, the dots disappeared more slowly (half-life, 3.2 min) than did the extravasation (half-life, 1.3 min). In addition to the @entity575 dots, 64% of the sites at which leukocytes were attached to the endothelium were stained with @entity575 . These sites were marked by @entity575 rings (diam, 3.4 +/- 0.2 microns) and were most numerous in the largest postcapillary venules (diam, 20-40 microns). Most (95%) of the @entity575 rings were located at intercellular junctions but usually were not sites of Monastral blue extravasation. The results indicate that endothelial gaps at intercellular junctions are focal openings, which occupy < 3% of the luminal surface and are distinct from sites of leukocyte attachment. The reduction in Monastral blue extravasation that precedes the closure of the gaps could result from a decrease in the driving force for the convective movement of the tracer or from a decrease in the conductance of the gaps, perhaps due to the accumulation of sievelike substances within the gaps.
