Regular article :AATEX3(1):17-27
The usage of chick embryos for studying the mechanism of cardiovascular malformations caused by chemicals was studied. Caffeine (CA), well known as a teratogen for the cardiovascular system of chick embryos, was administered at the dose of 3.0 mg per egg to chick embryos from two different breeds between incubation day 2 (ID2, H-H stage 14) and 5 (H-H stage 27). The eggs were incubated until ID12 to examine the cardiovascular malformation. Treatment at H-H stage 19 (ID3) was highly lethal and treatment at this stage and at stages 23-24 (ID4) induced a high degree of cardiovascular malformation in the embryos from both breeds. The embryotoxicity caused by CA in the two different breeds similarly varied with the developmental stage of treatment. Phenobarbital (PB), also a teratogen, was administered to chick embryos during H-H stages 22-24 at the doses of 1.13, 2.25 and 4.5 mg/egg to compare its embryotoxicity with that caused by treatment with CA. PB at the dose of 2.25 mg/egg or more was highly lethal and induced cardiovascular malformation. Administration of 13 jug of adenosine (AD) before CA and PB treatment reduced the lethality of PB but the effects of CA and teratogenicity of PB were not changed. However, in cultured cardiac cells at H-H stages 22-24 the frequency of spontaneous cell beating increased by treatment with 5 and 10 ƒÊM CA and decreased by that with 20 ƒÊM CA and those effects were reduced by co-administration of 0.5 ƒÊM AD. PB at the concentration of 6 ƒÊM or more reduced the frequency of cell beating and its effect was not changed by co-administration of 0.5 ƒÊM AD. Th responses to CA and PB treatment in whole chick embryos and cultured cardiac ceils were different. We believe that chick embryos can produce reproducible data when the developmental stage is precisely judged and the interactions of some chemicals on whole embryos and selected tissue or cells can be easily examined, so that they are very convenient to explore the mechanism of teratogenicity of chemicals.