A quantitative analysis of glucagon binding to isolated intact neonatal and adult rat hepatocytes on the basis of two different binding models

Pingoud, Vera; Peters, Frens; Haas, T; Trautschold, I.

doi:10.1016/0304-4165(82)90153-2

Cited by 22 publications

(8 citation statements)

References 25 publications

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“…Hence, the data are inconsistent with either positive or negative cooperativity with respect to the glucagon-receptor interaction. The results thus confirm those of Pingoud et al (1982) determined on isolated hepatocytes.…”

Section: Discussionsupporting

confidence: 87%

“…In contrast, negative cooperativity (Hill coefficient <1) or apparent negative cooperativity caused by receptor heterogeneity has been reported for glucagon binding to liver plasma membranes of rats (Sperling et al, 1980) and mice (Lafuse & Edidin, 1980) and for glucagon binding to isolated rat hepatocytes (Sonne et al, 1978(Sonne et al, , 1982. In contrast, Pingoud et al (1982) have recently reported lack of cooperativity with binding to isolated hepatocytes.…”

Section: Discussionmentioning

confidence: 89%

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Noncooperative receptor interactions of glucagon and eleven analogs: inhibition of adenylate cyclase

Rd¹,

Wt²,

Flanders³

et al. 1983

Biochemistry

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Glucagon and 11 glucagon derivatives were characterized and compared with respect to the cooperativity of their receptor interactions and their ability to elicit a biphasic (activation-inhibition) response from the adenylate cyclase system of rat liver plasma membranes. Slope factors were evaluated from two sets of experimental data, binding to hepatocyte receptors and activation of adenylate cyclase. The results are consistent with noncooperative binding to a single affinity state of the glucagon receptor for all derivatives, irrespective of the modification and the agonist properties of the derivatives. High-dose inhibition of adenylate cyclase activity was observed for native glucagon and all of the derivatives which were examined at high concentrations (greater than 10(-5) M). Partial agonism of some low-affinity glucagon derivatives is not caused by high-dose inhibition. Several mechanisms which might give rise to high-dose inhibition such as receptor cross-linking or multivalent receptor binding are discussed in relationship to the glucagon-receptor interaction. These phenomena indicate that significant differences exist between the glucagon system and the beta-adrenergic system.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 89%

Noncooperative receptor interactions of glucagon and eleven analogs: inhibition of adenylate cyclase

Rd¹,

Wt²,

Flanders³

et al. 1983

Biochemistry

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“…Since the complex binding of glucagon to plasma membrane receptors has not been uniformly observed (7,8) and since both negative and positive homotropic interactions have been suggested to play roles in the binding of glucagon to receptor (4,9,10), the validity of mathematical models involving two populations of glucagon receptors has yet to be placed within a biochemical framework. Nevertheless, the hepatic glucagon receptor has been identified as a protein with an apparent molecular weight of 60,000 (11)(12)(13)(14), and other studies have demonstrated (i) the interaction of the receptor with additional membrane components during hormonal activation of adenylyl cyclase and (ii) the importance of GTP in both increasing the activity of that enzyme and decreasing the affinity of the receptor for glucagon (9,(15)(16)(17)(18)(19).…”

mentioning

confidence: 99%

Identification of distinct receptor complexes that account for high-and low-affinity glucagon binding to hepatic plasma membranes.

Mason¹,

Tager²

1985

Proc. Natl. Acad. Sci. U.S.A.

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We have analyzed ligand-receptor complexes resulting from (i) the incubation of canine hepatic plasma membranes with [12'I5iodoglucagon and (ii) subsequent gentle solubilization of receptor-bound ligand with digitonin. The complexes (molecular weight 500,000) retain the radiolabeled ligand during gel filtration and subsequent manipulation at 40C in the absence of covalent crosslinking. Affinity chromatography of the glucagon-receptor complexes on columns of wheat germ lectin linked to agarose resulted in two fractions, one of which was not bound by the column and the other of which was specifically eluted by N-acetylglucosamine. The presence of GTP during the incubation of plasma membranes with [125I]iodoglucagon caused about a 50% decrease in total ligand binding but affected only the ligand-receptor complexes that bound to wheat germ lectin. Moreover, it was found that the proportion of the two forms of ligand-receptor complexes identified by chromatography on wheat germ lectin depended on the degree of saturation of the membrane receptor. Thus, both the inhibition by glucagon of radiolabeled glucagon binding to membranes and the concomitantly decreased extent of association of the radiolabeled ligand with solubilized receptor complexes could be modeled in terms of two noninteracting receptor populations (having dissociation constants of about 0.35 and 4.94 x 10-9 M). We conclude that (i) glucagon-receptor complexes formed on canine hepatic plasma membranes exist in two forms that differ after solubilization by digitonin in their avidities for wheat germ lectin, (a) the highand low-affinity binding of glucagon characteristic of hepatic plasma membranes arises from distinct receptor populations that probably differ in glycosylation, and (Uii) the effect of GTP to decrease binding of glucagon to membranes arises from interactions of the nucleotide with the receptor complex that binds to wheat germ lectin.Although the binding ofligand to plasma membrane receptors is known to initiate the mechanism of peptide hormone action, many details ofligand-receptor interactions remain to be clarified. Such interactions often fail to conform to those expected for single binding equilibria, and it has been noted that this deviation from the simple case is particularly acute in the binding of glucagon to hepatic plasma membranes and to surface receptors of isolated hepatocytes (1-6): as much as a 50,000-fold increase in the concentration of hormone is required to cause a reduction from 90% to 10% of maximal binding of [125I]iodoglucagon, whereas theory predicts that a 100-fold increase should be sufficient for a single binding equilibrium. In fact, the complex binding of glucagon both to rat hepatocytes and to canine hepatocytes has been successfully modeled in terms of two noninteracting populations of receptors having different affinities for the ligand (1, 3, 5). In the case of canine hepatocytes, cells that appear to bind glucagon with a notable degree of complexity, high-and low-affinity receptor populations were...

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“…There have been several reports concerning the ontogeny of glucagon receptors in tissues such as liver and heart [2,3], The number of glucagon receptors is known to be lower in the fetus and newborn and to increase grad ually to reach adult levels during the first few weeks of life [4]. In spite of several reports regarding the ontogénie pattern of peptide hormone receptors, there is some inconsis tency in various studies on the maturation of the post-receptor complex axis, which in volves the guanosine-5'-triphosphate (GTP) regulatory and catalytic components [5,6].…”

Section: Introductionmentioning

confidence: 99%

Effect of Dexamethasone on the Adenylate Cyclase System of Cultured Hepatocytes of Fetal Rats

Nishida¹,

Takeuchi²

1987

Neonatology

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During treatment of primary cultured hepatocytes with dexamethasone for several hours, cyclic AMP formation and glycolysis by glucagon increased dose dependently. In the cells pretreated with dexamethasone, the output of intracellular cyclic AMP increased significantly (p < 0.01) with glucagon of 2.8 × 10^––⁹M or more, and the amount of glucose released also increased significantly (p < 0.01) with glucagon of 2.8 × 10^––8M or more, compared to the control cells. Moreover, treatment with dexamethasone increased the stimulatory effect of guanosine-5′-triphosphate (GTP), guanyl-5′-yl-imidodiphosphate on adenylate cyclase and significantly increased the stimulatory effect of fluoride. In the rat hepatocytes primarily cultured with dexamethasone for several hours, the stimulatory effect of GTP and fluoride on adenylate cyclase increased time dependently. These data indicate that the glucocorticoid regulates the sensitivity of adenylate cyclase at distinct loci of the post-receptor system.

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A quantitative analysis of glucagon binding to isolated intact neonatal and adult rat hepatocytes on the basis of two different binding models

Cited by 22 publications

References 25 publications

Noncooperative receptor interactions of glucagon and eleven analogs: inhibition of adenylate cyclase

Noncooperative receptor interactions of glucagon and eleven analogs: inhibition of adenylate cyclase

Identification of distinct receptor complexes that account for high-and low-affinity glucagon binding to hepatic plasma membranes.

Effect of Dexamethasone on the Adenylate Cyclase System of Cultured Hepatocytes of Fetal Rats

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