Effect of pineal indoles on the chick embryo

In a study on the embryotoxicity of pineal indoles on developing chick embryos in vivo, the pineal indoles--namely, melatonin (MEL), methoxytryptamine (MTA) and methoxytryptophol (MTP)--were injected into the yolk sacs of the chick embryos through the air chambers of the eggs on the 4th day of incubation. The eggs were opened and the embryos examined after 6, 10 or 14/15 days of incubation. Abnormalities were found to occur mainly in the 6- and 10-day-old embryos, which exhibited external malformations such as twisted vertebral column, abdominal hernia, exteriorization of heart and viscera, defects of eye, beak and limb. From the results obtained from embryos on the 14th or 15th day of incubation, MEL was found to be the most toxic indole in regard to the mortality induced, whereas MTA had the highest teratogenicity because of the frequent incidence of abnormal embryos. Effect of MTP treatment on the development of chick embryos varied greatly between doses, and there were no abnormal embryos found on the 14th or 15th day of incubation.