Abstract
Two types of somatomedin/insulin-like growth factor (SM/IGF) receptors have been defined. Type I receptors have a higher affinity for SM-C/IGF than IGF-II and bind insulin at high concentrations. Type II receptors have a higher affinity for IGF-II than SM-C/IGF I , and do not bind insulin. In this study we have characterized the binding ofIGF-II to human monolayer fibroblast cultures. 125I-IGF-II binds to the human fibroblasts with anaverage specific binding of 12,5% /200,000 cells. The binding of IGF-I was 25% and of insulin was 4,5% of the specific IGF-II binding. The IGF-II was bound to a high affinity receptor. Half maximal displacement was seen with 12 ng/ml IGF-II and 45 ng/ml IGF-I. Insulin at high concentration caused no displacement. The estimated affinity of the IGF-II receptor was 1,2 nM with calculated 400,000 receptor sites/cell. No autoregulation of these IGF-II receptors was seen by homologous hormone. Serum deprivation led to a 50% increase in IGF-II receptor sites. IGF-II binding to human fibroblasts fits the criteria for a type II receptor. There are more receptors for IGF-II on these cells than for either IGF-I or insulin. This suggests an important metabolic role for IGF-II in normal human fibroblasts.
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Thorsson, A., Hintz, R., Enberg, G. et al. Receptors for Insulin-like Growth Factor II on human fibroblast monolayers. Pediatr Res 18, 1211 (1984). https://doi.org/10.1203/00006450-198411000-00064
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DOI: https://doi.org/10.1203/00006450-198411000-00064
