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  • Title: Ca2+ -uptake into noradrenaline-storing granules of bovine splenic nerves.
    Author: Burger A, Bellersheim M.
    Journal: Naunyn Schmiedebergs Arch Pharmacol; 1976 Dec; 296(1):47-57. PubMed ID: 189227.
    Abstract:
    Noradrenaline-storing granules, a mitochondrial fraction and a microsomal fraction of bovine splenic nerve trunks were prepared by differential centrifugation. These particulate fractions were characterized by their noradrenaline content, succinate dehydrogenase and glucose-6-phosphatase activity. In the presence of ATP-Mg2+ all three fractions accumulated 45Ca2+ during incubation with 0.1 mM 45 CaCl2, buffered with potassium phosphate or glycylglycine (pH 7.5; 28 degrees C). The accumulated 45 Ca2+ was not removable by EGTA, and the uptake was absent at 0 degrees C or after destruction of the particles by sonication. The behaviour of the 45 Ca2+ -uptake into all three fractions against varying ATP-concentrations, metabolic inhibitors (pentachlorophenol, desaspidine, 2,4-dinitrophenol, N-ethylmaleimide, p-chloromercuribenzoate, sodium azide, amobarbital) and drugs (phenoxybenzamine, verapamil, prenylamine, reserpine, bretylium, phentolamine) was studied. Under nearly all conditions there were differences between the 45 Ca2+ -uptake into mitochondria and that into microsomes, which suggests two distinct uptake processes. The 45 Ca2+ -uptake into the granule fraction behaved intermediate between the two other fractions under many conditions, but not under all. Therefore, it is not possible to explain the 45 Ca2+ -uptake into the granule fraction as being due to contamination with mitochondria and microsomes; an inherent ATP-Mg2+ -dependent 45Ca2+ -uptake into the nerve granules must be postulated, which is not directly coupled with the noradrenaline transport into these particles. A particulate fraction (14000-100000 g), containing noradrenaline granules, was prepared from the vas deferens of the rat. Incubation with 5 X 10(-6) M (-)-noradrenaline and 0.1 mM 45Ca2+ showed that the particles of this fraction take up noradrenaline and 45Ca2+. The uptake of both was dependent on ATP-Mg2+. The ATP-Mg2+ -dependent uptake of both noradrenaline and 45Ca2+ was substantially reduced in the corresponding tissue fraction prepared from denervated vasa deferentia.
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