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Degranulation of mast cells in the chick chorioallantoic membrane does not increase macromolecular extravasation
V Rizzo1, J Z Shumko, D O Defouw
1Department of Anatomy, Cell Biology, and Injury Sciences, UMDNJ, New Jersey Medical School, Newark 07103-2714, USA.
Objective:
To test the hypothesis that stimulation of mast cell degranulation during normal angiogenesis in the chick chorioallantoic membrane (CAM) serves to acutely activate macromolecular transendonelial pathways.
Methods:
Using shell-less cultures of 6-day-old chick embryos, efflux of fluorescein isothiocyanate (FITC)-dextran 150 from CAM microvessels was evaluated, after applications of compound 48/80 or exogenous histamine, by computer-assisted videodensitometric analyses. Real-time confocal imaging enabled optical differentiation of first-order pre- and postcapillaries from the capillary networks. Cytologic ultrastructure of the microvascular units was also evaluated.
Results:
Although endogenous histamine was measurable and its concentration was increased after application of compound 48/80, segmental endothelia of the CAM microvascular units consistently restricted extravasation of FITC-dextran 150. Furthermore, intravascular injections of histamine also failed to induce interendothelial gap formation or macromolecular flux across the segmental CAM endothelia.
Conclusions:
These results are consistent with the interpretation that histamine-activated transendothelial pathways are inactive in the CAM at day 6. Whether such inactivity serves to retard facilitation of CAM angiogenesis by activated mast cells remains to be tested.