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

MPG-Autoren
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Almers,  Wolfhard
Department of Molecular Cell Research, Max Planck Institute for Medical Research, Max Planck Society;

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Zitation

Thomas, P., Wong, J. G., Lee, A. K., & Almers, W. (1993). A low affinity Ca2+ receptor controls the final steps in peptide secretion from pituitary melanotrophs. Neuron, 11(1), 93-104. doi:10.1016/0896-6273(93)90274-U.


Zitierlink: http://hdl.handle.net/11858/00-001M-0000-0019-AA39-F
Zusammenfassung
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 microM. 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/micron2.