| First Author | Smith RM | Year | 1993 |
| Journal | Biol Reprod | Volume | 49 |
| Issue | 1 | Pages | 1-12 |
| PubMed ID | 8353175 | Mgi Jnum | J:13286 |
| Mgi Id | MGI:61489 | Doi | 10.1095/biolreprod49.1.1 |
| Citation | Smith RM, et al. (1993) Mouse preimplantation embryos exhibit receptor-mediated binding and transcytosis of maternal insulin-like growth factor I. Biol Reprod 49(1):1-12 |
| abstractText | High-resolution microscopy in conjunction with colloidal gold-labeled insulin-like growth factor I (IGF-I) has been used to provide evidence that the IGF-I receptor is first detected in 8-cell-stage mouse embryos, confirming the results of previous reverse transcriptase polymerase chain reaction (RT-PCR) studies. Specificity for the IGF-I receptor was demonstrated by displacement with unlabeled IGF-I and dual-labeling experiments with colloidal gold-labeled or unlabeled insulin. Labeled IGF-I ligand is internalized by means of receptor-mediated endocytosis following its concentration in coated pits, and it can be visualized within cytoplasmic organelles. Immunocytochemical analyses at the blastocyst stage, using gold-labeled antibodies to the receptor, confirmed the expression of IGF-I receptors on all cells of the embryo. Similar studies with antibodies directed against the ligand demonstrated that IGF-I internalized by the embryo in vivo is maternally derived. Approximately 40% of blastocysts showed apical plasma membrane binding of gold-labeled ligand (responders), while approximately 60% did not demonstrate binding (nonresponders); however, both classes of embryo expressed receptors on basolateral membranes of trophectoderm cells and on the surface of inner masses. Functional studies show that incubating embryos in physiological levels of IGF-I (40 ng/ml) results in increased numbers of cells in the inner cell mass (p < 0.05), but not the trophectoderm, as compared to controls. |
