Preimplantation mouse embryos internalize maternal insulin via receptor-mediated endocytosis: Pattern of uptake and functional correlations

Trophoblast phagocytic program: roles in different placental systems

“…This process seems to be closely associated with intake of small particle and fluid for embryo nutrition, but have also been suggested to participate in the embryo attachment to the uterus (Enders, 1976) and transport of crucial survival factors from the mother organism to the embryo, such as insulin and IGF-I insulin growth factor I (Heyner et al, 1989;Smith et al, 1993). Endocytosis of extracellular material requires a receptor-mediated pathway and specific regulatory mechanisms.…”

Developmental regulation and the role of insulin and insulin receptor in metanephrogenesis

“…3B). Such mitogenic effects have been observed in various cell culture systems and preimplantation embryos (8,14), and the effects in individual organ systems either have not been investigated or insulin was found to be inhibitory for cell growth (33,34). The latter effect may be due to the interference in the IGF-I-IGF-IR interaction by the insulin at its higher concentrations (1).…”

“…However, the role of insulin and its receptor in embryonic development has received limited attention, which in part may be related to the fact that insulin and its receptor are primarily known for their regulation of glucose metabolism rather than as growth modulators (6). Nonetheless, the binding of insulin to the preimplantation mouse embryos, and expression of insulin receptor (IR) in the prepancreatic͞precardiac stage of avian embryos and in early mid-gestational human fetuses raises the possibility for the growth potential of insulin (7)(8)(9)(10). Furthermore, the expression of insulin during the prepancreatic stage at sites other than the pancreas-i.e., liver and yolk sacsuggests that insulin may play a role in mammalian embryonic development (11,12).…”

Recent advances in developmental genetics: Growth factors and morphogens

“…This work was extended when it was found (Rosenblum et al, 1986;Heyner et al, 1989) that the preimplantation embryo, starting at the morula stage, has insulin receptors and can internalize maternal insulin (from fallopian and uterine fluid) by receptor-mediated endocytosis. The addition of IGF I, unlike the addition of other types of growth factors, had no beneficial effect on the development of mouse preimplantation embryos cultured singly in large volumes of culture media (Paria and Dey, 1990), while others have found that exogenous IGF I (Harvey and Kaye, 1992;Rappolee et al, 1992) and IGF I1 increased cell number in blastocysts (Rappolee et al, 1992).…”