Essential role of the polyamines in early chick embryo development.

The polyamines putrescine, spermidine and spermine were analyzed in chick embryos during the first 2 days of development. A rapid increase in the activity of ornithine decarboxylase (ODC), the initial and rate-limiting enzyme in polyamine synthesis, was observed immediately after onset of incubation. Peak activities were found at 15 and 23 h of incubation. The first peak coincides with gastrulation and the second peak with early neurulation in the embryo. All three polyamines varied in a similar manner as did ODC, with putrescine and spermidine at about the same level and spermine at a lower level. The ODC activity was blocked by alpha-difluoromethylornithine, an enzyme-activated irreversible inhibitor. The inhibitor was administered to embryos in ovo at 5 h of incubation, i.e. prior to the first major increase in ODC activity. This block prevented the accumulation of the polyamines and inhibited development as gastrulation, suggesting a decisive role for polyamines in this developmental event.