The chick embryo yolk-sac blood vessel system as an experimental model for irritation and inflammation

Experimental studies on the incubated egg, for example the embryo and the chorioallantoic membrane (CAM), are carried out frequently. The yolk-sac blood vessel system, the first system supplying the embryo, has not yet been used in toxicological studies. This paper describes experiments with ethanol and sodium hydroxide to test the application of this blood vessel system in the assessment of toxic effects. The experiments were carried out at day 4 of incubation. Different concentrations of the test substances were applied directly on yolk-sac. The acute reaction, mainly haemorrhages, was recorded semi-quantitatively up to 5 min post-application (p.a.). The results revealed a clear concentration dependency and marked differences between the two substances. During the late reaction up to 3 days p.a., repair processes occurred showing signs of a granulation tissue, including angiogenesis and the development of collagenous fibres. These experiments show the functional ability of the yolk-sac blood system for toxicological tests. Additionally, this system has some advantages compared with the CAM, for example the immaturity of the embryo nervous system and the possibility to evaluate findings on the embryo itself.