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UPTAKE OF CALCIUM BY CHROMAFFIN GRANULES IN VITRO
Author(s) -
Kostron H.,
Winkler H.,
Geissler D.,
König P.
Publication year - 1977
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1977.tb10419.x
Subject(s) - incubation , calcium , centrifugation , chemistry , density gradient , differential centrifugation , in vitro , chromaffin cell , biochemistry , biophysics , chromatography , biology , adrenal medulla , endocrinology , catecholamine , physics , organic chemistry , quantum mechanics
— Partly purified chromaffin granules were incubated in vitro with Ca 2+ (with trace amounts of 45 Ca 2+ ) in concentrations ranging from 4 μm to 1 mm. After incubation the granules were washed with media containing EDTA and then subjected to density gradient centrifugation (1.3 to 2.0 m‐sucrose solutions) in order to characterize the particles which had taken up 45 Ca 2+ . By using marker enzymes and various inhibitors of Ca 2+ uptake into such cell particles as mitochondria it was established that under the conditions of the experiments chromaffin granules took up Ca 2+ from the incubation medium. To characterize this uptake a simplified density gradient procedure was tested and found to be suitable. The uptake of Ca 2+ into chromaffin granules was strongly dependent on temperature. It was not activated by ATP. The uptake was linear up to 10 min. At high calcium concentrations (above 200 μm) the rate of uptake levelled off. The uptake at 37°C was 1 nmol Ca 2+ /mg protein/min at a Ca 2+ concentration of 500 μm. Mg 2+ had no influence on Ca 2+ uptake, whereas Sr 2+ (1 mm) inhibited it. The methods established in this study should prove useful for a further characterization of this Ca 2+ uptake into chromaffin granules which is likely to represent a useful model for the Ca 2+ uptake occurring in the intact gland.