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- Burgess, G.M., et al.
(author)
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Further studies on the interactions between the calcium mobilization and cyclic AMP pathways in guinea pig hepatocytes
- 1986
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In: Molecular Pharmacology. - : American Society for Pharmacology and Experimental Therapeutics. - 0026-895X .- 1521-0111. ; 30:4, s. 315-320
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Journal article (peer-reviewed)abstract
- Isoproterenol (50 nM) potentiated the effects of angiotensin (1-50 nM) on 86Rb efflux and 45Ca efflux from guinea pig hepatocytes. This effect occurred in the presence or absence of extracellular Ca2+ and required the simultaneous presence of both isoproterenol and angiotensin. Neither the divalent cationophore, A23187, nor 4 beta-phorbol dibutyrate could substitute for angiotensin. The effects of isoproterenol were greatest with submaximal concentrations of angiotensin, whereas maximal concentrations of angiotensin were affected little. Isoproterenol did not substantially increase the formation of [3H]inositol triphosphate or the ratio of isomers [3H]inositol 1,4,5-trisphosphate and [3H]inositol 1,3,4-trisphosphate formed in response to angiotensin. Isoproterenol also enhanced the phase of Ca2+ mobilization involving Ca2+ entry which is consistent with the previously proposed functional linkage between receptor-regulated Ca2+ release and Ca2+ entry. These findings suggest that isoproterenol may act by increasing the sensitivity of the endoplasmic reticulum to the Ca2+-releasing action of inositol 1,4,5-trisphosphate.
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- Connolly, Eamonn, et al.
(author)
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Norepinephrine-induced Na+ influx in brown adipocytes is cyclic AMP-mediated
- 1986
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In: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 261:31, s. 14377-14385
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Journal article (peer-reviewed)abstract
- To examine the involvement of Na+ ions in adrenergic responses in brown adipose tissue, a method is described for measuring Na+ influx into isolated brown adipocytes, using short (30 s) incubations with 22Na+, followed by a two-step centrifugation recovery procedure. Using this method, a clear norepinephrine-stimulated accumulation of intracellular 22Na+ was observed, which was enhanced by the addition of ouabain, was insensitive to amiloride (a Na+/H+ exchange blocker), and could not be mimicked by the total removal of oxygen from the incubation medium. The norepinephrine-stimulated Na+ influx was dose-dependent for the hormone with an EC50 of 250 nM, was blocked by the beta-antagonist propranolol but not by the alpha 1-antagonist prazosin, and could be induced by adrenergic agonists with the order of potency: isoproterenol greater than norepinephrine greater than phenylephrine, indicating a beta-receptor-mediated process. The Na+ influx was found to be cAMP-dependent since it could be induced by both theophylline (a phosphodiesterase inhibitor) and forskolin (an adenylate cyclase activator), but it was independent of other known cellular cAMP-dependent responses since neither addition of fatty acid substrates (octanoate or palmitate), nor of the mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone could induce the phenomenon, despite having significant stimulatory effects on cellular respiration. Furthermore, total respiratory inhibition with rotenone, or total oxygen depletion of the medium with dithionite, did not prevent the normal norepinephrine-induced Na+ influx. The possibility that this beta-mediated norepinephrine-stimulated Na+ influx plays an important physiological role in brown adipose tissue activity is discussed, perhaps as one of the, as yet undefined, signals initiating tissue growth in the chronically beta-stimulated tissue of animals facing long-term increases in thermogenic demands.
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| 7. |
- Edvardsson, Bo, et al.
(author)
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Service and Quality - An introduction
- 1989
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In: Quality Development in Private and Public Service Companies. - : Natur and Kultur, Stockholm.
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Journal article (peer-reviewed)
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| 10. |
- Lopez-Rivas, Abelardo, et al.
(author)
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Ca2+-mobilizing actions of platelet-derived growth factor differ from those of bombesin and vasopressin in Swiss 3T3 mouse cells
- 1987
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In: Proceedings of the National Academy of Sciences of the United States of America. - : The National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 84:16, s. 5768-5772
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Journal article (peer-reviewed)abstract
- Addition of the mitogenic peptides bombesin and vasopressin to quiescent Swiss 3T3 mouse cells increased the cytosolic Ca2+ concentration without any measurable delay. In contrast, there was a significant lag period (16 +/- 1.2 s) before platelet-derived growth factor (PDGF) increased cytosolic Ca2+ concentration. This lag was not diminished at high concentrations of either porcine or human PDGF. Similar results were obtained in 3T3 cells loaded with quin-2 or fura-2. The differences in the effects of bombesin, vasopressin, and PDGF on Ca2+ movements were also substantiated by measurements of 45Ca2+ efflux and of cellular 45Ca2+ content. Activation of protein kinase C by phorbol esters inhibited Ca2+ mobilization induced by either bombesin or vasopressin. In contrast, phorbol esters had no effect on PDGF-induced cytosolic Ca2+ concentration increase or acceleration of 45Ca2+ efflux. Finally, bombesin and vasopressin caused a rapid increase in the production of inositol 1,4,5-trisphosphate and inositol 1,3,4-trisphosphate, whereas PDGF, even at a saturating concentration, exerted only a small effect. These results indicate that the signal transduction pathways activated by PDGF that lead to Ca2+ mobilization can be distinguished from those utilized by bombesin and vasopressin.
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