Insulin binding and action in isolated rat hepatocytes: Evidence for spare receptors

Frank, H. J. L.; Davidson, Mayer B.; P, Serbin

doi:10.1016/0026-0495(81)90035-4

Cited by 23 publications

(13 citation statements)

References 27 publications

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“…There was no accumulation of glycogen in these cells during incubation in agreement with other reports studying hepatocytes incubated with glucose [23][24][25].…”

Section: Discussionsupporting

confidence: 93%

“…The former denotes impaired sensitivity and the latter decreased responsiveness to insulin [27]. Since hepatocytes have spare insulin receptors [23], the diminished capacity of the high affinity, low capacity receptor can explain the impaired sensitivity. The decreased responsiveness is due to a post-receptor defect [27].…”

Section: Discussionmentioning

confidence: 99%

“…Incubations were carried out for 90 min at 20 ~ with periodic shaking. Bacitracin (2.4 mmol/1), included in all incubations, has a minimal effect on insulin binding at 20 ~ [23].…”

Section: Binding Studiesmentioning

confidence: 99%

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Hepatocyte insulin binding and action in rats with sommatomammotrophic tumours

Davidson

Melmed

1983

Diabetologia

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Summary. The effects of chronic elevations of growth hormone levels on hepatic insulin binding and action were studied in rats with subcutaneously implanted growth hormoneproducing tumours. These animals were significantly heavier (p < 0.001 ; 388 _+ 29 versus 239_+ 4 g), had elevated insulin levels, (6.8 _ 0.6 versus 3.3 _ 0.5 ng/ml), lower glucose concentrations (6.0_+ 0.4 versus 9.3 _ 0.5 mmol/1) and larger hepatocyte diameters (28.7_ 0.6 versus 24.0_+ 0.4 p~m) and surface areas (2661 + 119 versus 1835 + 65 am 2) than control rats. Insulin binding and action [net (C~4)-glucose incorporation into glycogen] were compared in hepatocytes isolated from these two groups. Because of the difference in hepatocyte size, insulin binding was normalized for cell surface area. Binding of the tracer alone (0.9 _+ 0.05 versus 1.3 _+ 0.12%/cm:) and capacity of the high affinity, low capacity receptor (30.9_+ 5.9 versus 65.2 _+ 5.9 sites/Ixm 2) were significantly decreased (p < 0.02) in tumour-bearing rats. Dose-response curves of insulin action in hepatocytes chronically exposed to excess growth hormone were shifted to the fight. The maximal response was also significantly decreased. However, the relation between the amount of insulin bound and the proportion of the maximum insulin effect obtained were similar in cells from the two groups. Thus, in rat hepatocytes chronically exposed to excess growth hormone, both a receptor and a post-receptor defect occur while the insulin receptor itself functions normally. Material and MethodsGH3 cells were supplied by the American Type Culture Collection (Bethesda, Maryland). These cells are an established clonal strain of rat pituitary tumour cells secreting both GH and prolactin [12]. Cells were maintained in monolayer culture in a humidified atmosphere of 95% air -5% CO2 using Dulbecco's modified Eagle's medium (DMEM) supplemented with horse serum (15%), fetal calf serum (2.5%), penicillin (50 U/ml), streptomycin (50 p~g/ml) and glutamine (5 mmol/1) (Irvine Scientific, Santa Ana, California). For tumour generation, approximately 5-7 • 106 cells derived from the same parent culture were harvested by trypsinization, washed and resuspended in DMEM containing penicillin (50 U/ml) and streptomycin (50 p~g/ml). An aliquot of the cell suspension was counted in an automatic cell counter (Coulter Electronics, Hialeah, Florida), and the suspension was diluted to -106 cells/ml. One ml was injected SC into female Wistar-Furth rats as described previously [11]. Tumours were palpable by the end of 4 weeks. Control rats were treated similarly except that they received the media alone. Tumour-bearing and control rats were sacrificed alternately 6-8 weeks after inoculation.Rats were anaesthetized with sodium pentobarbital (60 mg/kg). A cannula was placed in the portal vein to prepare isolated hepatocytes (see below) but before the perfusion was started, blood was sampled from the inferior vena cava via a small needle attached to a syringe. Glucose concentrations were measured by a glucose oxidase met...

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“…There was no accumulation of glycogen in these cells during incubation in agreement with other reports studying hepatocytes incubated with glucose [23][24][25].…”

Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

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Hepatocyte insulin binding and action in rats with sommatomammotrophic tumours

Davidson

Melmed

1983

Diabetologia

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“…Still, the content of IR in cells can impact insulin signal transduction and the biological response to insulin. Previously, the recognition that the maximal response to insulin was elicited under conditions of less than complete IR binding (occupancy) led to a "spare receptor theory" [16]. While some investigators have postulated that with spare IR, moderate changes in IR number or even function might not impact insulin action, the studies of IR knockout mice described above demonstrate that a reduction in tissue IR content has a significant physiological impact.…”

Section: Physiological Regulation Of the Irmentioning

confidence: 96%

Regulation of insulin receptor function

Youngren¹

2007

Cell. Mol. Life Sci.

172

118

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Resistance to the biological actions of insulin contributes to the development of type 2 diabetes and risk of cardiovascular disease. A reduced biological response to insulin by tissues results from an impairment in the cascade of phosphorylation events within cells that regulate the activity of enzymes comprising the insulin signaling pathway. In most models of insulin resistance, there is evidence that this decrement in insulin signaling begins with either the activation or substrate kinase activity of the insulin receptor (IR), which is the only component of the pathway that is unique to insulin action. Activation of the IR can be impaired by post-translational modifications of the protein involving serine phosphorylation, or by binding to inhibiting proteins such as PC-1 or members of the SOCS or Grb protein families. The impact of these processes on the conformational changes and phosphorylation events required for full signaling activity, as well as the role of these mechanisms in human disease, is reviewed in this article.

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“…Since these receptor types may have different levels of functional significance, larger affinity variations in those receptor types of lesser concern (often the low affinity receptors) could be acceptable. Additionally, some biopharmaceuticals (e.g., insulin and leutinizing hormone (Frank et al, 1981;Mendelson et al, 1975)) have spare receptors (i.e., receptors which exist in excess of those required to produce a maximal PD effect (Bourne and von Zastrow, 2004). Binding affinity differences for these products may pose less of a concern if biopharmaceutical target occupancy is suitable to induce a comparable pharmacological response.…”

Section: Defining a Pharmacologically Relevant Speciesmentioning

confidence: 99%