Insulin action in early embryonic life: anti-insulin receptor antibodies retard chicken embryo growth but not muscle differentiation in vivo.

Insulin receptors are present in chicken embryos at day 2 of development and insulin stimulates embryonic growth and differentiation. Most important, anti-insulin antibodies cause either death or developmental retardation in chicken embryos of that age. To determine if the embryo's endogenous insulin acts through its own receptor, we compared the effects of anti-insulin antibodies to the effects of anti-insulin receptor antibodies on growth and differentiation indexes in the chicken embryo. While the anti-insulin antibody caused a dose-dependent decrease in growth parameters like weight, total protein, DNA, RNA, total creatine kinase activity and a marker of differentiation, the creatine kinase-MB, the anti-insulin receptor antibody decreased all parameters except the creatine kinase-MB. Many, but not all, of the effects of insulin in early embryos, thus, are mediated through the insulin receptor.