Effect of local shell conductance on the vascularisation of the chicken chorioallantoic membrane.

The vascularisation of the chorioallantoic membrane (CAM) of avian embryos is influenced by environmental oxygen partial pressure (P(O(2))) on a global level: incubation at high P(O(2)) reduces the density of pre- and post-capillary vessels of the CAM and decelerates the thinning of the blood-gas barrier, and vice versa. This study investigates the effects of local P(O(2)) on vascular development during the formative period of days ten to fifteen, by making half of the egg hypoxic and the other half hyperoxic. The densities of arterioles, venules and capillaries were reduced under the hypoxic side, compared to untreated eggs, but not significantly changed on the hyperoxic side. Harmonic mean thickness of the tissue barrier and total CAM blood volume were not affected by the treatments. Vascular development of the CAM was therefore only partly influenced by local P(O(2)).