Endothelial gaps: time course of formation and closure in inflamed venules of rats

Abstract

In the rat trachea, substance P causes rapid but transient plasma leakage. We sought to determine how closely the number, morphology, and size of endothelial gaps correspond to the time course of this leakage. Endothelial gaps were examined by scanning electron microscopy (EM), by transmission EM, or by light microscopy after silver nitrate staining. Substance P-induced leakage of the particulate tracer Monastral blue peaked at 1 min but decreased with a half-life of 0.3 min. The number of silver-stained gaps also peaked at 1 min then decreased significantly more slowly (half-life 1.9 min) than the leakage. Scanning EM revealed two types of endothelial gaps, designated vertical gaps and oblique slits. Vertical gaps predominated at peak leakage, whereas oblique slits became more common as the leakage diminished. Measurements of the mean diameter of vertical gaps made by light microscopy, scanning EM, and transmission EM were all in the range of 0.36-0.47 micron. Fingerlike endothelial cell processes that appeared during gap formation became shorter as the leakage diminished (mean length: 1.44 microns at 1 min compared with 1.06 microns at 3 min after substance P), suggesting a role in gap closure. We conclude that the plasma leakage occurring immediately after an inflammatory stimulus results from the rapid formation of endothelial gaps. Multiple factors, including alterations in gap morphology, gap closure, and changes in driving force, are likely to participate in the rapid decrease in the leakage.

Vascular Permeability and Pathological Angiogenesis in Caveolin-1-Null Mice

“…36,37,42 Others have reported leakage through a paracellular route, independent of VVOs. 43,44 In CVH, yet another type of blood vessel, the "mother" vessel, accounts for the bulk of vascular hyperpermeability. 45 Mother vessels are greatly enlarged, thin-walled, pericyte-poor sinusoids that derive from pre-existing normal venules after longer exposures to VEGF and other angiogenic stimuli.…”

In vivo high-efficiency transcoronary gene delivery and Cre–LoxP gene switching in the adult mouse heart

“…Accordingly, we assessed a series of vascular permeabilizing agents other than histamine and found that substance P (SP) 33 was well tolerated by the mouse. Gene expression rate with 2 ng SP was 41.179.8% (mean7s.d., n¼4), with 5 ng SP it was 56.4714.5% (n¼5), and with 100 ng SP it was 28.272.5% (n¼2); the latter dose and an even higher dose prolonged recovery time; so a total dose of 5 ng was used in all subsequent experiments.…”

Intravenously administered oligonucleotides can be delivered to conducting airway epithelium via the bronchial circulation

“…Only 150 mg/kg increased leakage and was therefore chosen as the most effective dose. [14][15][16][17][18][19][20]. None of the doses tested altered leakage in the parenchyma.…”

“…10 Inflammatory mediators have previously been shown to cause the formation of gaps up to 500 nm between bronchial endothelial cells. 18,19 We, therefore, developed a model of bronchial microvascular leakage using the inflammatory mediators PAF, histamine and bradykinin, in an attempt to open the gaps between the bronchial endothelial cells and allow more LPD complexes to escape from the bronchial vasculature. Although the combined optimized doses of PAF and histamine significantly increased leakage in the larynx/trachea and main bronchi, the mediators did not increase LPD escape from the bronchial vasculature.…”

“…[14][15][16][17] Inflammatory mediators have previously been shown to cause the formation of gaps up to 500 nm between bronchial endothelial cells in rat and dog airways. 18,19 Previous studies have shown that inflammatory mediators increase the delivery of gene transfer agents to other tissues. [20][21][22] Here, we evaluated the effects of three inflammatory mediators, platelet-activating factor (PAF), histamine and bradykinin and assessed whether the most effective inflammatory mediator(s) could increase escape of LPD and 'naked' ODNs from the bronchial circulation and consequently, increase transfection of the conducting airway epithelium.…”