Insulin stimulates protein synthesis in compacted mouse embryos.

Preliminary work suggested that insulin affects preimplantation mouse embryos. We investigated the effects of insulin on incorporation of [3H]-leucine by embryos cultured for long (greater than 24 h) or short (4 h) terms with insulin. Insulin stimulated incorporation by compacted 8-cell embryos, blastocysts and expanded blastocysts. The stimulation in blastocysts had an EC50 of 0.5 pM in the presence of 1 g/L BSA and was blocked by anti-human insulin anti-serum. Inclusion of insulin in the medium elevated the levels of incorporation towards those of embryos developing in vivo. The stimulation was not observed in uncompacted 8-cell embryos. The ontogeny of stimulation at compaction coincides with a switch in energy dependence from lactate and pyruvate to glucose and an increase in protein synthetic activity.