Effect of Trypan Blue on Rat Embryos

Abstract

THE teratogenic effect of trypan blue in pregnant rats has been well established^1–3. The dye appears to be most active when injected at 8½ days of pregnancy and gives rise to a variety of abnormalities involving almost all the systems of the embryo. Of a number of chemically related azo dyes tested, trypan blue was found to be the most active teratogenic agent in rats⁴ and it has also been shown to act as a teratogen in other rodents^5–7 and in chicks⁸. Three main hypotheses explaining its action have been proposed. The first assumed that a part, at least, of the dye enters the blastocyst and acts directly on the embryonic cells⁹; the second postulates a ‘clogging’ of the yolk sac epithelium with the large dye molecules, thus inhibiting the transfer of essential substances to the conceptus ; the third suggests maternal metabolic changes resulting in the formation of substances which are responsible for the fœtal malformations.