Degranulation of mast cells in the chick chorioallantoic membrane does not increase macromolecular extravasation during normal angiogenesis.
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.
Rizzo
V
V
Department of Anatomy, Cell Biology, and Injury Sciences, UMDNJ, New Jersey Medical School, Newark 07103-2714, USA.
Shumko
J Z
JZ
Defouw
D O
DO
D000482:Allantois / Q000098:blood supply* / Q000166:cytology; D000818:Animals; D015550:Cell Degranulation; D002642:Chick Embryo; D002823:Chorion / Q000098:blood supply* / Q000166:cytology; D003720:Densitometry; D003911:Dextrans / Q000378:metabolism; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects; D006632:Histamine / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D008407:Mast Cells / Q000502:physiology*; D008833:Microcirculation; D008854:Microscopy, Electron; D018715:Microscopy, Video; D018919:Neovascularization, Physiologic / Q000502:physiology*; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D003911:Dextrans; C015219:fluorescein isothiocyanate dextran; D003189:p-Methoxy-N-methylphenethylamine; D006632:Histamine; D016650:Fluorescein-5-isothiocyanate