Calcium loading of secretory granules in stimulated neurohypophysial nerve endings

Neuroscience
S ThirionG Nicaise

Abstract

The total calcium content of secretory granules, Cag, was evaluated in isolated neurohypophysial nerve endings. The Cag in the resting state, as measured by X-ray microanalysis, is relatively high with an average of 7.4 +/- 0.6 mmol/kg wet weight. Following a depolarizing potassium challenge, a subpopulation of granules with even higher Cag could be detected, dispersed over a wider range of concentrations (up to 70 mmol/kg wet weight). After subsequent rinsing in physiological saline, Cag decreased to control values. This could have resulted from Ca2+ extrusion, or from preferential secretion of calcium-enriched granules. Our data can be interpreted in favor of the second explanation since no decrease in Cag was observed when secretion was blocked by a hyperosmotic saline. The effect of hyperosmotic conditions on isolated nerve endings was further studied by monitoring free cytoplasmic Ca2+ with the calcium-sensitive dye Fura-2 and by conventional electron microscopy. It was demonstrated that hyperosmotic treatment alone did not increase basal cytosolic Ca2+ concentrations but did significantly reduce the potassium-induced cytosolic rise in Ca2+. Electron microscopy of nerve endings in hyperosmotic conditions showed numerous ex...Continue Reading

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Citations

Mar 17, 1999·Proceedings of the National Academy of Sciences of the United States of America·S ThirionG Nicaise
Aug 4, 2006·Journal of Neurophysiology·Babak A KachoeiNeil S Magoski
Mar 10, 2001·Reviews in the Neurosciences·P K Panegyres
May 28, 2014·The Journal of General Physiology·James M McNallyJosé R Lemos
Dec 22, 1999·Cell Calcium·S RaisonG Nicaise
Mar 28, 2018·International Journal of Molecular Sciences·Andrea Gerbino, Matilde Colella
Nov 3, 2016·F1000Research·Matilde ColellaSilvana Curci
Mar 28, 1998·The Journal of Biological Chemistry·P BelanA V Tepikin
Jul 21, 1998·The Journal of Biological Chemistry·W J ScheenenC Fasolato

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