Increased insulin receptor binding in erythrocytes from growth hormone-deficient children

1991 ◽  
Vol 11 (4) ◽  
pp. 195-201 ◽  
Author(s):  
N. Dávila ◽  
B. Barceló ◽  
M. C. Carranza ◽  
C. Calle
Keyword(s):  
Growth Hormone ◽  
Dissociation Constant ◽  
Gh Deficiency ◽  
High Capacity ◽  
Insulin Binding ◽  
Scatchard Analysis ◽  
Site Model ◽  
Binding Data ◽  
Receptor Concentration ◽  
Normal Sensitivity

Erythrocytes from growth hormone-deficient children (GHd-children) (n=10) showed a statistically significant increase in insulin binding at low unlabeled insulin concentrations, together with a threefold decrease in apparent receptor affinity, as compared to control children (C) (n=11). Scatchard analysis of the binding data using the two-site model revealed that both the receptor concentration R1 [GHd-children 0.10±0.01 ng/ml and C 0.03±0.002 ng/ml] and the dissociation constant KD1 [GHd-children (0.48±0.05)×10−9M and C (0.19±0.01)×10−9M] for high affinitylow capacity sites were significantly increased in erythrocytes from GHd-children, while neither receptor concentrations (R2) nor the dissociation constant (KD2) for low affinity-high capacity sites proved to be altered. These events were accompanied by a normal sensitivity to insulin as well as glucose tolerance in the GHd-group. The meaning of the increased insulin binding with normal insulin sensitivity in GH-deficiency is discussed.

Chronic and endogenous regulation of insulin receptors by catecholamines in adipocytes from patients with a phaeochromocytoma

1990 ◽  
Vol 10 (2) ◽  
pp. 201-207 ◽  
Author(s):  
M. C. Carranza ◽  
M. A. Simón ◽  
A. Torres ◽  
C. Calle
Keyword(s):  
Adipose Tissue ◽  
Binding Sites ◽  
Insulin Receptors ◽  
Human Adipose Tissue ◽  
Insulin Binding ◽  
Scatchard Analysis ◽  
Cooperative Model ◽  
Receptor Affinity ◽  
Site Model ◽  
Binding Data

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.

scholarly journals Modeling Analysis of [11C]Flumazenil Kinetics Studied by PET: Application to a Critical Study of the Equilibrium Approaches

1993 ◽  
Vol 13 (3) ◽  
pp. 454-468 ◽  
Author(s):  
Jacques Delforge ◽  
André Syrota ◽  
Michel Bottlaender ◽  
Marina Varastet ◽  
Christian Loc'h ◽  
...  
Keyword(s):  
Dissociation Constant ◽  
Benzodiazepine Receptors ◽  
Basic Relation ◽  
Critical Study ◽  
Model Parameters ◽  
Scatchard Analysis ◽  
Equilibrium Dissociation Constant ◽  
Receptor Concentration ◽  
Equilibrium Dissociation

The multi-injection modeling approach was used for the in vivo quantitation of benzodiazepine receptors in baboon brain using positron emission tomography (PET) and [11C]flumazenil (RO 15-1788) as a specific ligand. The model included three compartments (plasma, free, and bound ligand) and five parameters (including the benzodiazepine receptor concentration). The plasma concentration after correction for the metabolites was used as the input function. The experimental protocol consisted of four injections of labeled and/or unlabeled ligand. This protocol allows the evaluation, from a single experiment, of the five model parameters in various regions of interest. For example, in the temporal cortex, the concentration of receptor sites available for binding ( B′max) and the equilibrium dissociation constant ( Kd) were estimated to be 70 ± 15 pmol/ml and 15.8 ± 2.2 n M, respectively. The validity of the equilibrium approach, which is the most often used quantitation method, has been studied from simulated data calculated using these model parameters. The equilibrium approaches consist of reproducing in PET studies the experimental conditions that permit the use of the usual in vitro methods such as Scatchard analysis. These approaches are often open to criticism because of the difficulty of defining the notion of equilibrium in in vivo studies. However, it appears that the basic relation of Scatchard analysis is valid over a broader range of conditions than those normally used, such as the requirement of a constant bound/free ratio. Simulations showed that the values of the receptor concentration ( B′max) and the equilibrium dissociation constant ( Kd) found using Scatchard analysis are always underestimated. These simulations also suggest an explanation concerning the dependency of B′max and Kd on the time point employed for the Scatchard analysis, a phenomenon found by several authors. To conclude, we propose new protocols that allow the estimation of the B′max and Kd parameters using a Scatchard analysis but based on a protocol including only one or two injections. These protocols being entirely noninvasive, it thus becomes possible to investigate possible changes in receptor density and/or affinity in patients.

STUDIES ON THE BINDING OF 125I-LABELLED CORTICOTROPHIN TO ISOLATED RAT ADRENOCORTICAL CELLS

1975 ◽  
Vol 64 (1) ◽  
pp. 175-184 ◽  
Author(s):  
R. A. J. McILHINNEY ◽  
D. SCHULSTER
Keyword(s):  
Dissociation Constant ◽  
Adrenal Glands ◽  
Direct Evidence ◽  
Scatchard Analysis ◽  
Adrenocortical Cells ◽  
Binding Characteristics ◽  
Whole Cells ◽  
High Affinity ◽  
Binding Data ◽  
Normal Rat

SUMMARY Isolated adrenocortical cells, prepared by collagenase disaggregation of normal rat adrenal glands, have been used to study the binding characteristics of 125I-labelled corticotrophin (ACTH) of established biological activity. The binding of the labelled hormone to these whole cells was highly specific, only peptides possessing steroidogenic activity displaced the labelled hormone. Binding was rapid, being complete within 5 min of adding the hormone, and the amount of hormone bound remained constant for up to 20 min thereafter. Over the range 160–10000 pg ACTH/ml, increased binding of the hormone was observed at all concentrations of hormone which stimulated steroidogenesis. However at levels of ACTH which stimulated maximal steroidogenesis there was no saturation of binding. This provides the first direct evidence for the existence of 'spare receptors' for ACTH on whole adrenocortical cells. Scatchard analysis of the binding data suggests that there are two types of receptor for ACTH in this preparation of cells. One receptor is of high affinity (dissociation constant = 2·5 × 10−10 mol/l) about 3000 sites/cell and the other is of lower affinity (dissociation constant = 1 × 10−8 mol/l) with about 30000 sites/cell.

Effect of calcium on [125I]insulin binding to rat adipocytes

1978 ◽  
Vol 56 (9) ◽  
pp. 843-848 ◽  
Author(s):  
Kappu S. Desai ◽  
Bernard Zinman ◽  
George Steiner ◽  
Charles H. Hollenberg
Keyword(s):  
Specific Binding ◽  
High Capacity ◽  
Insulin Binding ◽  
Dissociation Rate ◽  
Extracellular Calcium ◽  
Scatchard Analysis ◽  
Rat Adipocytes ◽  
High Affinity ◽  
Receptor Sites ◽  
High Affinity Receptor

The specific binding of [125I]insulin to rat adipocytes was reduced in the absence of extracellular calcium. The addition of calcium to the calcium-free medium during incubation restored [125I]insulin binding towards normal. The specific binding of insulin was significantly increased with calcium concentrations as low as 0.5 mM and maximal binding occurred with 5 mM calcium. Scatchard analysis of the data suggests two major binding sites, one a high-affinity low-capacity site (Kd, 1.5 × 1010 M−1) and the other a lower-affinity high-capacity site (Kd, 4.7 × 109 M−1). There was a 50% decrease in the number of high-affinity sites in absence of extracellular calcium. The dissociation curve of receptor-bound insulin was nonlinear both in the absence and presence of extracellular calcium suggesting receptor heterogeneity. The dissociation rate of receptor-bound insulin was greater when insulin was bound in the absence of extracellular calcium than in its presence. These results indicate that extracellular calcium, by increasing the number of high-affinity receptor sites, can alter the the ratio of high-affinity to low-affinity receptors for insulin in adipocytes.

Insulin binding to Leydig cells and insulin levels in testicular interstitial fluid at different stages of development in the rat

1991 ◽  
Vol 128 (3) ◽  
pp. 375-381 ◽  
Author(s):  
G. Grizard ◽  
M. Fournet ◽  
N. Rigaudière ◽  
N. Lombard-Vignon ◽  
J. Grizard
Keyword(s):  
Leydig Cells ◽  
Plasma Insulin ◽  
Interstitial Fluid ◽  
Insulin Binding ◽  
Scatchard Analysis ◽  
Stages Of Development ◽  
Insulin Levels ◽  
Binding Data ◽  
Plasma Insulin Levels ◽  
Specific Insulin

ABSTRACT Binding of insulin to purified intact Leydig cells (LC) and LC membranes, and levels of insulin in plasma and testicular interstitial fluid (IF) were quantitatively evaluated in rats at three stages of development. Specific insulin binding to intact LC increased significantly with age. Scatchard analysis of the binding data always gave curvilinear plots; the number of high affinity binding sites/LC were 2590±514, 3977±701 and 8342±2039 at 21, 40 and 70 days respectively. When the results were expressed per μg membrane protein, the maximal specific insulin binding also increased between 21 and 40 days but did not significantly change thereafter. With ageing, insulin levels in testicular IF decreased (3·05±0·30, 2·48±0·22 and 1·66±0·13 μg/l in 21-, 40- and 70-day-old rats) whereas plasma insulin increased. Taken together, these results suggest (1) that the intratesticular environment in this hormone cannot be evaluated by plasma insulin levels—testicular IF insulin concentration is probably a better index and (2) that insulin may play a role in the development of LC function during sexual maturation. Journal of Endocrinology (1991) 128, 375–381

The Binding of Calcium Ions to Bovine Factor X by Rate Dialysis

1978 ◽  
Vol 40 (02) ◽  
pp. 350-357
Author(s):  
Robert H Yue ◽  
Menard M Gertler
Keyword(s):  
Molecular Weight ◽  
Dissociation Constant ◽  
Calcium Ions ◽  
Activation Process ◽  
Factor X ◽  
The Real ◽  
High Affinity ◽  
Binding Data ◽  
Sequential Mechanism ◽  
Bovine Factor

SummaryThe binding of Ca+2 to bovine factor X (molecular weight of 74,000) (Yue und Gertler 1977) was studied by the technique of rate dialysis and with the use of 45Ca+2. The binding data are consistent with a model of sequential mechanism. One mole of Ca+2 binds to the glycoprotein with a dissociation constant of 5.2 × 10-5 M and an additional 39 ± 4 moles of Ca+2 bind to this zymogen with a dissociation constant of 3.7 × 10-3M. The binding of the high affinity Ca+2 causes a functionally significant change in the zymogen, and (calcium) (factor X) complex is the real substrate in the activation process by the protease in Russell’s viper venom.

Calcium and the Fc Receptor on Human Platelets

1987 ◽  
Vol 57 (03) ◽  
pp. 298-301
Author(s):  
William F Clark ◽  
Gerald J M Tevaarwerk ◽  
Bruce D Reid ◽  
Suzanne Hall ◽  
Anita Caveney ◽  
...  
Keyword(s):  
Specific Binding ◽  
Normal Subjects ◽  
Human Platelets ◽  
Fc Receptor ◽  
Normal Male ◽  
Scatchard Analysis ◽  
Normal Female ◽  
Apparent Difference ◽  
Binding Data ◽  
Direct Binding

SummaryWe have described the calcium dependence of the IgG Fc receptor (Fc-R) on human platelets by analyzing the direct binding of radiolabelled Fc fragments, monomers and dimers of IgG. Specific binding to platelets was undetectable at 37° C in a calcium-free preparation but readily detected when calcium was restored. Scatchard analysis of the binding data for the calcium-restored platelets permitted calculation of the available Fc-R and the Ka of binding for the different IgG ligands. The mean Ka of binding for 12 normal subjects varied from 107 to 108 L/M, with an equal receptor number measured by Fc fragments and dimers of IgG, but a lesser amount for monomeric IgG. There was no apparent difference in Fc-R number for platelets from 6 normal male versus 6 normal female subjects.At 4° C binding was detectable for dimers and polymers of IgG in a calcium-free preparation and this was markedly increased with recalcification. Thus, our data are consistent with an Fc receptor population on human platelets whose avidity for binding is significantly enhanced in a calcium-restored medium.

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