Inhibitory effects of anti-angiogenic agents on neovascularization and growth of the chorioallantoic membrane (CAM). The possibility of a new CAM assay for angiogenesis inhibition.

Protamine sulfate and combinations of heparin-cortisone acetate known as having anti-angiogenic activities impaired the growth of chorioallantois at the dose inducing no decrease in growth rate of the embryos. This inhibitory effect of the agents is presumed to be mediated by the specific inhibition of the growth of endothelial cells forming chorioallantoic blood vessels based on the following results: significant correlations were found between the length of CAM vessels measured by an automatic image analyzer and the estimated volumes of chorioallantois (correlation coefficient r = 0.94) and these agents specifically inhibited the (3H)-thymidine incorporation into cultured endothelial cells at the dose having no effects on that into cultured chick embryonic cells. On the other hand, all DNA-synthesis inhibitors, mitomycin C, 5-fluorouracil, and paraformaldehyde suppressed the growth of both CAM and embryo and resulted in early embryonic death, which might be due to the nonspecific impairment of DNA synthesis by these agents. These results indicate the possibility that the present CAM assay could screen agents having anti-angiogenic activity.