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  • 1
    Electronic Resource
    Electronic Resource
    Effect of adrenal steroids on insulin release from cultured rat islets of Langerhans (1986)
    Springer
    Diabetologia 29 (1986), S. 119-121 
    Details
    ISSN: 1432-0428
    Keywords: Insulin release ; insulin biosynthesis ; dexamethasone ; prednisolone ; hydrocortisone ; aldosterone ; cultured islets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of additions to the culture medium of some natural or synthetic corticosteroid hormones was studied in cultured rat islets of Langerhans. The steroids decreased glucose-induced insulin release. The extent of inhibition by dexamethasone was 18–55%, prednisolone 23%, hydrocortisone 21% and aldosterone 18%. None of them affected the basal secretion of insulin or had any effect on diameter or insulin content of the islet. The inhibitory action of dexamethasone on insulin release was observed in the range 63 nmol/l to 6.3 μmol/l. At 6.3 μmol/l during two h, dexamethasone (a) inhibited insulin response to glucose concentrations above 5 mmol/l (b) caused a delay in the first phase and markedly reduced the second phase of insulin release of perifused islets, and (c) decreased the incorporation of [H3]-leucine into total islet proteins without affecting [H3]-leucine-incorporation into insulin plus proinsulin. It is suggested that steroids, by directly acting on the islets of Langerhans, may modulate the insulin-release response to secretagogues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00456122
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  • 2
    Electronic Resource
    Electronic Resource
    Insulin secretory responses of a clonal cell line of simian virus 40-transformed B cells (1986)
    Springer
    Diabetologia 29 (1986), S. 727-733 
    Details
    ISSN: 1432-0428
    Keywords: Cell line ; insulin secretion ; HIT cells ; B cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have evaluated the potential of the clonal insulin-secretory cell line HIT-T15 as a model system for investigating stimulus-secretion coupling in pancreatic B cells. In contrast to other cell lines, HIT cell insulin secretion was consistently stimulated 2- to 3-fold by D-glucose. The maximally effective concentration of glucose was 10 mmol/1; between 2 and 10 mmol/l glucose the increase in insulin release was paralleled by an increased rate of glucose oxidation. The main characteristics of glucose-stimulated insulin release by HIT cells were essentially similar to those of normal islets. Thus, the response was (1) specific for metabolizable sugars (D-mannose and D-glyceraldehyde stimulated insulin release but L-glucose and D-galactose were ineffective); (2) markedly dependent on extracellular Ca2+ concentration; (3) potentiated by forskolin, glucagon, acetylcholine and 12-0-tetradecanoyl phorbol 13-acetate; (4) inhibited by adrenaline or somatostatin; (5) showed a biphasic pattern of release in perifusion experiments, with both phases being potentiated by forskolin. The secretory response of the HIT cells to amino acids was also similar to that of normal islets. Thus, L-leucine and its deamination product 2-ketoisocaproate were effective stimuli, whereas L-isoleucine and L-glutamine were ineffective. Insulin release from HIT cells could also be evoked by the sulphonylureas glibenclamide and tolbutamide and by an increase in concentration of extracellular K+ to 40 mmol/1. The content of cyclic AMP in HIT cells was increased modestly by glucose but not by an increase in extracellular K+. Forskolin elicited a 4-fold increase in cyclic AMP content. We conclude that HIT cells retain the essential features of the insulin secretory response of normal B cells and represent an important tool for further biochemical characterisation of the secretory system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00870283
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  • 3
    Electronic Resource
    Electronic Resource
    The hypoglycaemic and insulinotropic activity of Tinospora crispa: studies with human and rat islets and HIT-T15 B cells (1989)
    Springer
    Diabetologia 32 (1989), S. 354-359 
    Details
    ISSN: 1432-0428
    Keywords: Tinospora crispa ; insulin secretion ; hypoglycaemic ; insulinotropic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In Malaysia, Tinospora crispa extract is taken orally by Type 2 (non-insulin-dependent) diabetic patients to treat hyperglycaemia. We have evaluated the claimed hypoglycaemic property by adding aqueous extract to the drinking water of normal and alloxan-diabetic rats. After one week, fasting blood glucose levels were significantly (p〈0.01) lower and serum insulin levels were significantly (p〈0.01) higher in treated diabetic animals (10.4±1.0 mmol/l and 12.8±1.1 μU/ml respectively) compared to untreated diabetic controls (17.4±1.7 mmol/l and 8.0±0.7 μU/ml respectively). The insulinotropic action of T. crispa was further investigated in vitro using isolated human or rat islets of Langerhans and HIT-T15 cells. In static incubations with rat islets and HIT-T15 B cells, the extract induced a dosage dependent stimulation and potentiation of basal and glucose-stimulated insulin secretion respectively. This insulinotropic effect was also evident in perifused human and rat islets and HIT-T5 B-cells. The observations that (i) in all three models insulin secretory rates rapidly returned to basal levels on removal of the extract and (ii) in rat islets, a second challenge with T. crispa induced an additional, stimulated response, are all consistent with physiological release of insulin by B cells. Moreover, the rate of HIT-T15 glucose utilisation was not affected by incubation with T. crispa, suggesting that the cells were viable throughout. These are the first studies to provide biochemical evidence which substantiates the traditional claims for an oral hypoglycaemic effect of Tinospora crispa, and which also show that the hypoglycaemic effect is associated with increased insulin secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277258
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  • 4
    Electronic Resource
    Electronic Resource
    ATP-sensitive K-channels in HIT T15 β-cells studied by patch-clamp methods, 86Rb efflux and glibenclamide binding (1989)
    Springer
    Pflügers Archiv 415 (1989), S. 47-55 
    Details
    ISSN: 1432-2013
    Keywords: Pancreaticβ-cell ; ATP-sensitive K-channel ; Sulphonylurea ; Glibenclamide ; Tolbutamide ; Diazoxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract ATP-sensitive K-channels in the cloned β-cell line HIT T15 were studied by patch-clamp methods; by measurement of 86Rb efflux; and by [3H]glibenclamide binding to isolated membrane preparations. In inside-out patches a 50 pS K-channel was found which was blocked by ATP or tolbutamide applied to the intracellular membrane surface. A minimum estimate of about 500 channels per β-cell was obtained by combining whole-cell and single-channel data. The rate of efflux of 86Rb from 86RbCl-loaded HIT cells was markedly increased by intracellular ATP-depletion; 86Rb-efflux was progressively inhibited by increasing concentrations of glibenclamide or tolbutamide. In non-ATP-depleted cells, diazoxide elicited a concentration-dependent stimulation of 86Rb-efflux which was completely blocked by 1 μM glibenclamide. Isolated membranes showed dose-dependent saturable binding of [3H]glibenclamide to both high (K d=1.12 nM) and low (K d=136 nM) affinity binding sites. We estimate about 5000 high-affinity binding sites per cell. [3H]-glibenclamide binding was inhibited by tolbutamide (IC50=125 μM) but was not affected by diazoxide. ADP (0.5 or 1.0 mM) markedly reduced binding; other nucleotides tested were ineffective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373140
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    Paper (German National Licenses)
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