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  • 1
    ISSN: 1432-1912
    Keywords: 45Ca2+ Influx ; Catecholamines ; 22Na+ Influx ; 86Rb+ Uptake ; Secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In bovine adrenal medullary cells, we reported that 22Na+ influx via nicotinic receptor-associated Na+ channels is involved in 45Ca2+ influx, a requisite for initiating the secretion of catecholamines (Wada et al. 1984, 1985b). In the present study, we investigated whether the inhibition of Na+-pump modulates carbachol-induced 22Na+ influx, 45Ca2+ influx and catecholamine secretion in cultured bovine adrenal medullary cells. We also measured 86Rb+ uptake by the cells to estimate the activity of Na+, K+-ATPase. (1) Ouabain and extracellular K+ deprivation remarkably potentiated carbachol-induced 22Na+ influx, 45Ca2+ influx and catecholamine secretion; this potentiation of carbachol-induced 45Ca2+ influx and catecholamine secretion was not observed in Na+ free medium. (2) Carbachol increased the uptake of 86Rb+; this increase was inhibited by hexamethonium and d-tubocurarine. In Na+ free medium, carbachol failed to increase 86Rb+ uptake. (3) Ouabain inhibited carbachol-induced 86Rb+ uptake in a concentration-dependent manner, as it increased the accumulation of cellular 22Na+. These results suggest that Na+ influx via nicotinic receptor-associated Na+ channels increases the activity of Na+, K+-ATPase and the inhibition of Na+, K+-ATPase augmented carbachol-induced Ca2+ influx and catecholamine secretion by potentiating cellular accumulation of Na+. It seems that nicotinic receptor-associated Na+ channels and Na+, K+-ATPase, both modulate the influx of Ca2+ and secretion of catecholamines by accomodating cellular concentration of Na+.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 324 (1983), S. 15-19 
    ISSN: 1432-1912
    Keywords: Adrenal medulla ; Catecholamine ; Secretion ; Calcium ion ; α2-Agonists ; α2-Adrenoceptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In adrenal medullary cells, carbachol evokes the secretion of catecholamines with simultaneous uptake of45Ca. Highly selective agonists for α2-adrenoceptors, clonidine, naphazoline, guanfacine, tramazoline and oxymetazoline inhibited carbachol evoked secretion of catecholamines in a dose-dependent manner. These α2-agonists also inhibited the uptake of45Ca evoked by carbachol with similar dose-response curve to inhibition of catecholamine secretion. On the contrary, highly selective agonists for α1-adrenoceptors, phenylephrine and norfenefrine did not inhibit the secretion of catecholamines and cellular uptake of45Ca. The inhibition by α2-agonists was not restored either by the increase in carbachol, or Ca concentrations, suggesting that the mode of inhibition was distinct from competition at cholinergic receptors or Ca-channels. It is likely that α2-agonists inhibited the secretion of catecholamines via the inhibition of Ca uptake which was probably caused through the activation of α2-adrenoceptors.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The salt Pt6(NH3)10Cl10(HSO4)4(MGSPOS) with the average valence of Pt 2.33 was prepared in powder form by means of partial oxidization of [Pt(NH3)4][PtCl4](MGS) substituting HSO4- for 1/6 of both ligands NH3 and Cl-. The electrical conductivity σ has a maximum at about 230 K and a minimum at about 280 K. Therefore, the conductivity σ is semiconductive with the gap energy 0.04 eV below 230 K, and metallic in the sense of dσ/dT 〈 0 between 230 and 280 K, and again semiconductive above 280 K. The thermal analysis by DSC shows only on heating, three anomalies, G at ∼150 K, A at ∼ 200 K, and B at ∼250 K. The exothermic anomaly A succeeding to the weak anomaly G indicates that a glass transition takes place, and endothermic anomaly B corresponds to a structural transition. These two transitions may correspond to the two metal-semiconductor transitions found in the σ measurement. The ac calorimetry shows a specific heat anomaly also only on heating.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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