Chronic and endogenous regulation of insulin receptors by catecholamines in adipocytes from patients with a phaeochromocytoma |
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Authors: | M. C. Carranza M. A. Simón A. Torres C. Calle |
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Affiliation: | (1) Departments of Biochemistry and Surgery, School of Medicine, Complutense University, E-28040 Madrid, Spain |
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Abstract: | Insulin binding in adipocytes from patients with a phaeochromocytoma (PH) approached that of the controls (C) at low and higher concentrations of unlabeled insulin. The apparent receptor affinity was unchanged (ED50: PH 0.50×10–9M and C0.60×10–9M). Scatchard analysis of the binding data using the negative cooperative model revealed a 46% decrease in the total number of receptors together with no changes in both K–e (PH 0.55×109M–1 and C 0.36×109M–1) and K–f (PH 0.13×109 M–1 and C 0.07×109 M–1). According to the two site model, an altered proportion in the two classes of insulin binding sites was detected. This was accompanied by a catecholamine-desensitization of the adipocytes to the antilipolytic action of insulin. These events could represent a final situation of a chronic and endogeneous regulation by high levels of catecholamines of insulin receptors in human adipose tissue. |
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Keywords: | insulin binding insulin action human adipocytes phaeochromocytoma |
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