Effects of Desoxypyridoxine and Vitamin B 6 on Development of the Chick Embryo. ∗

Abstract

Summary

Desoxypyridoxine (1000 fig) injected into eggs prior to the start of the incubation period resulted in 100% mortality of the embryos; this inhibition was prevented by simultaneous injection of any of the three forms of vitamin B₆. The ratio of vitamin to inhibitor which permitted approximately 50% of the embryos to produce live chicks was 1/20 for pyridoxal, 1/50 for pyridoxamine and 1/100 for pyridoxine.

When injected after 4 or more days of incubation, 1000 μg of desoxypyridoxine proved non-toxic. Higher levels injected at 6 days of incubation proved toxic but this toxicity could not be prevented by any of the 3 forms of vitamin B₆. A possible explanation for this observed variation in toxicity of desoxypyridoxine at different stages of incubation is offered. Pyridoxal hydrochloride and pyridoxine hydrochloride also proved toxic at high levels while pyridoxamine dihydro-chloride was not toxic at the highest level tested.

Neither nicotinic acid nor its amide affected the inhibitory action of desoxypyridoxine; negative results were also obtained when DL-alanine was injected alone or with nicotinic acid.

These experiments demonstrate that vitamin B₆ becomes essential for embryonic growth very early in the incubation period.