Little is known about hormonal regulation of substrate transport and metabolism in the mucosal lining of the small intestine. Because insulin regulates these functions in other tissues by binding to its receptor, we have investigated the presence of insulin receptors in canine small intestinal mucosa with basolateral membranes (BLM) and brush border membranes (BBM) prepared by sorbitol density centrifugation. A14-[125l]iodoinsulin was used to study binding and structural characteristics of specific insulin receptors in BLM. Analysis of receptors in BLM identified binding sites with high affinity (Kd 88 pM) and low capacity (0.4 pmol/mg protein) as well as with low affinity (Kd 36 nM) and high capacity (4.7 pmol/mg protein). Binding was time, temperature, and pH dependent, and 125l-labeled insulin dissociation was enhanced in the presence of unlabeled insulin. Cross-reactivity of these receptors to proinsulin, IGF-II, and IGF-I was 4,1.8, and <1%, respectively. Covalent cross-linking of labeled insulin to BLM insulin receptors with disuccinimidyl suberate revealed a single 135,000-Mr band that was completely inhibited by unlabeled insulin. There was a 16-fold greater specific binding of insulin to BLM (39.0 ± 2.4%) than to BBM (2.5 ± 0.6%). These results demonstrate the presence of a highly specific receptor for insulin on the vascular, but not the luminal, surface of the small intestinal mucosa in dogs, and suggest that insulinmay play an important role in the regulation of gastrointestinal physiology.
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Original Contribution|
October 01 1987
Identification and Characterization of Insulin Receptors in Basolateral Membranes of Dog Intestinal Mucosa
Ronald L Gingerich;
Ronald L Gingerich
Edward Mallinckrodt Department of Pediatrics and the Departments of Medicine and Pathology, Washington University School of Medicine
St. Louis, Missouri
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William R Gilbert;
William R Gilbert
Edward Mallinckrodt Department of Pediatrics and the Departments of Medicine and Pathology, Washington University School of Medicine
St. Louis, Missouri
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Patricia G Comens;
Patricia G Comens
Edward Mallinckrodt Department of Pediatrics and the Departments of Medicine and Pathology, Washington University School of Medicine
St. Louis, Missouri
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James R Gavin, III
James R Gavin, III
Edward Mallinckrodt Department of Pediatrics and the Departments of Medicine and Pathology, Washington University School of Medicine
St. Louis, Missouri
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Address correspondence and reprint requests to Dr. Ronald L. Gingerich, Department of Pediatrics, Washington University School of Medicine, P.O. Box 14871, St. Louis, MO 63178.
Diabetes 1987;36(10):1124–1129
Article history
Received:
July 28 1986
Revision Received:
March 31 1987
Accepted:
March 31 1987
PubMed:
3308583
Citation
Ronald L Gingerich, William R Gilbert, Patricia G Comens, James R Gavin; Identification and Characterization of Insulin Receptors in Basolateral Membranes of Dog Intestinal Mucosa. Diabetes 1 October 1987; 36 (10): 1124–1129. https://doi.org/10.2337/diab.36.10.1124
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