This study examines the ontogenesis of somatomedin and insulin receptors in man. Particulate plasma membranes were prepared by ultracentrifugation from various tissues removed from fetuses after abortion and classified as < 17, 17-25, and > 25 cm in length. The binding of iodinated insulinlike growth factors 1 (IGF-1) and 2 (IGF-2), somatomedin A (SMA), multiplication-stimulating activity (MSA), and insulin was examined at the different ages. In the liver, cross-reaction studies revealed separate insulin and IGF-2 receptors. The Scatchard plots of insulin binding to liver membranes were curvilinear and showed an increase in the concentration of insulin receptors with advancing age. A single IGF-2 receptor was found on liver and no alteration was observed during development. The brain contained a lower concentration of insulin receptors. A change in the brain receptors for somatomedins occurred during development. Early in gestation, a high concentration of a low-affinity IGF-1 receptor was found. After approximately the 17th wk of gestation a higher affinity IGF-1 receptor appeared, which then increased in concentration. Cross-reaction studies also revealed changes in the specificity of these receptors during development. In the youngest fetal group IGF-2 was preferentially bound. Around midgestation a separate IGF-1 receptor, indicated by the preferential displacement of iodinated IGF-1 by IGF-1, appeared. In contrast, iodinated IGF-2 bound to a receptor where IGF-1 and IGF-2 were equipotent.
CITATION STYLE
Sara, V. R., Hall, K., Misaki, M., Fryklund, L., Christensen, N., & Wetterberg, L. (1983). Ontogenesis of somatomedin and insulin receptors in the human fetus. Journal of Clinical Investigation, 71(5), 1084–1094. https://doi.org/10.1172/JCI110858
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