MAST-CELL ACTIVATION ACCELERATES THE NORMAL RATE OF ANGIOGENESIS IN THE CHICK CHORIOALLANTOIC MEMBRANE

Using shell-less cultures of chick embryos, the effect of mast cell de granulation on normal rates of angiogenesis in the chorioallantoic mem brane (CAM) was recorded from Day 6 to Day 9. Based on the centripetal ordering method with capillaries as the initial point of reference, t he first two orders of pre- and postcapillary microvessels were evalua ted. After infusion of compound 48/80 into the allantoic cavity, the n ormal proliferation rate of order-1 pre- and postcapillaries was marke dly increased. Increases of second-order vessel numerical densities (n umber/cm(2)) were less than those of the order-1 vessels. Thus, length densities (mean length x numerical density) were increased for the or der-1 Vessels only. During the accelerated rate of CAM angiogenesis, e ndothelial restriction of FlTC-dextran 150 remained uniformly high. He nce, secreted mast cell products likely worked synergistically with en dogenous CAM angiogenic factors between Days 6 and 9, without increasi ng rates of macromolecular extravasation. However, histamine injection into the allantoic cavity at Day 10, in conjunction with calcium supp lementation of the shell-less cultures at Day 9, elevated the rate of FITC-dextran 150 extravasation. Whether differentiation of this transe ndothelial pathway is required for enhancement of CAM angiogenesis aft er Day 10 remains uncertain. (C) 1996 Academic Press, Inc.