A low affinity Ca2+ receptor controls the final steps in peptide secretion from pituitary melanotrophs

Thomas, Paul, Wong, J. G., Lee, A. K. and Almers, W. (1993) A low affinity Ca2+ receptor controls the final steps in peptide secretion from pituitary melanotrophs. Neuron, 11 (1). pp. 93-104. ISSN 0896-6273

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Abstract

Using flash photolysis of caged Ca2+ and the membrane capacitance to monitor exocytosis, we have studied the response of single melanotrophs to a step rise in cytosolic Ca2+ concentration ([Ca2+]i). Exocytosis begins with a rapid burst. This burst is followed by a slower phase, which is inhibited at cytosolic pH 6.2, and an ultraslow phase, which is strongly temperature sensitive. The exocytic burst starts with a delay of 6–11 ms and continues at a rate that grows steeply with [Ca2+]i and is half-maximal at [Ca2+]i = 27 μM. At least 3 Ca2+ ions are required to trigger exocytosis. The rate constant at saturating [Ca2+]i suggests that exocytosis of a dense core vesicle takes 40 ms after all Ca2+ ions have bound to their regulatory sites. If docked dense core vesicles cause the exocytic burst, they must decorate the plasma membrane at a mean density of 0.5/μm2.

Item Type: Article
Faculty \ School: Faculty of Science
Depositing User: LivePure Connector
Date Deposited: 03 Mar 2020 09:09
Last Modified: 22 Apr 2020 14:40
URI: https://ueaeprints.uea.ac.uk/id/eprint/74381
DOI: 10.1016/0896-6273(93)90274-U

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