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- Gustafsson, Amanda Jabin, et al.
(författare)
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ADP ribose is an endogenous ligand for the purinergic P2Y1 receptor
- 2011
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Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 0303-7207 .- 1872-8057. ; 333:1, s. 8-19
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism by which extracellular ADP ribose (ADPr) increases intracellular free Ca2+ concentration ([Ca2+](i)) remains unknown. We measured [Ca2+](i) changes in fura-2 loaded rat insulinoma INS-1E cells, and in primary beta-cells from rat and human. A phosphonate analogue of ADPr (PADPr) and 8-Bromo-ADPr (8Br-ADPr) were synthesized. ADPr increased [Ca2+](i) in the form of a peak followed by a plateau dependent on extracellular Ca2+. NAD(+), cADPr, PADPr, 8Br-ADPr or breakdown products of ADPr did not increase [Ca2+](i). The ADPr-induced [Ca2+](i) increase was not affected by inhibitors of TRPM2, but was abolished by thapsigargin and inhibited when phospholipase C and IP3 receptors were inhibited. MRS 2179 and MRS 2279, specific inhibitors of the purinergic receptor P2Y1, completely blocked the ADPrinduced [Ca2+](i) increase. ADPr increased [Ca2+](i) in transfected human astrocytoma cells (1321N1) that express human P2Y1 receptors, but not in untransfected astrocytoma cells. We conclude that ADPr is a specific agonist of P2Y1 receptors.
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| 2. |
- Gustafsson, Amanda Jabin, et al.
(författare)
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Ryanodine receptor-operated activation of TRP-like channels can trigger critical Ca2+ signaling events in pancreatic beta-cells
- 2005
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Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 19:2, s. 301-303
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Tidskriftsartikel (refereegranskat)abstract
- There is little information available concerning the link between the ryanodine (RY) receptors and the downstream Ca(2+) signaling events in beta-cells. In fura-2 loaded INS-1E cells, activation of RY receptors by 9-methyl 5,7-dibromoeudistomin D (MBED) caused a rapid rise of [Ca(2+)]i followed by a plateau and repetitive [Ca(2+)]i spikes on the plateau. The [Ca(2+)]i plateau was abolished by omission of extracellular Ca(2+) and by SKF 96365. In the presence of SKF 96365, MBED produced a transient increase of [Ca(2+)]i, which was abolished by thapsigargin. Activation of RY receptors caused Ca(2+) entry even when the ER Ca(2+) pool was depleted by thapsigargin. The [Ca(2+)]i plateau was not inhibited by nimodipine or ruthenium red, but was inhibited by membrane depolarization, La(3+), Gd(3+), niflumic acid, and 2-aminoethoxydiphenyl borate, agents that inhibit the transient receptor potential channels. The [Ca(2+)]i spikes were inhibited by nimodipine and ryanodine, indicating that they were due to Ca(2+) influx through the voltage-gated Ca(2+) channels and Ca(2+)-induced Ca(2+) release (CICR). Activation of RY receptors depolarized membrane potential as measured by patch clamp. Thus, activation of RY receptors leads to coherent changes in Ca(2+) signaling, which includes activation of TRP-like channels, membrane depolarization, activation of the voltage-gated Ca(2+) channels and CICR.
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| 3. |
- Hoa, Nguyen Khanh
(författare)
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Assessment of anti-diabetic effect of Vietnamese herbal drugs
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The prevalence of type 2 diabetes mellitus is increasing in Vietnam as well as in other developing countries (China, Indian subcontinent, and Africa). Searching for hypoglycemic agents with origin from domestic herbals was considered as a useful way to find novel therapy of the disease. After treatment i.p. or orally of normal mice with extract of Anemarrhena asphodeloides (A.a.), Angiopteris evecta (A.e.) and Gynostemma pentaphyllum (G.p.), blood glucose levels of the mice were decreased. All of those 3 extracts also suppressed the rise in blood glucose in normal mice during a glucose tolerance test. At both 3.3 and 16.7 mM glucose, 2, 4 and 8 mg/ml Anemarrhena asphodeloides (A.a. or TH2) increased the insulin release of Wistar (W) and Goto- Kakizaki (GK) rat islets. In perifusions of islets, A.a. also increased insulin secretion that returned to basal levels when A.a. was omitted from the perifusate. Thus, ethanol extract of the roots of A.a. contains a substance, TH2, that stimulates insulin secretion from islets of normal W and GK rats. The mechanism behind TH2-stimulated insulin secretion involves an effect on the exocytotic machinery of the B-cell, mediated via pertussis toxin-sensitive Ge-proteins. G.p. extract had a hypoglycemic effect in rats and mice. We have isolated the active compound, phanoside, a gypenoside with molecular mass of 914.5 Da. When given orally to rats, phanoside (40 and 80 mg/kg) improved glucose tolerance and enhanced plasma insulin levels. Phanoside stimulated insulin release at 3.3 and 16.7 mM glucose from isolated rat pancreatic islets of both W and GK rats. Interestingly, B- cell sensitivity to phanoside is higher at 16.7 mM than at 3.3 mM glucose, since significant insulin responses were observed with phanoside between 31.25 and 125 μM only at the high glucose levels. When W rat islets were incubated at 3.3 mM glucose with 150 μM phanoside and 0.25 mM diazoxide to keep K-ATP channels open, insulin secretion was similar to that in islets incubated in 150 μM phanoside alone. At 16.7 mM glucose, phanoside-stimulated insulin secretion was reduced in the presence of 0.25 mM diazoxide. In W islets depolarized by 50 mM KCl and with diazoxide, phanoside stimulated insulin release 2-fold at 3.3 mM glucose but did not further increase the release at 16.7 mM glucose. When using nimodipine to block L-type Ca2+ channels in B-cells, phanoside-induced insulin secretion was unaffected at 3.3 mM glucose but decreased at 16.7 mM glucose. In perifusion of islets, phanoside (75 and 150 μM) dose- dependently increased insulin secretion that returned to basal levels when phanoside was omitted. Thus, the effect of phanoside seems to be exerted distal to K-ATP channels and L-type Ca2+ channels that is on the exocytotic machinery of the B-cells. In conclusion, from 8 Vietnamese herbal drugs, we have found 3 extracts which decreased blood glucose of the mice. Two of them (A.a and G.p. extract) stimulated insulin secretion from rat islets. Ethanol extract of A.a. (TH2) stimulated insulin secretion by an effect on the exocytotic machinery of the B cell mediated via pertussis toxin sensitive Ge-protein. From G.p. we islolated a novel substance, phanoside, that directly stimulates the exocytosis of insulin.
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