ISSN:
1059-910X
Keywords:
Secretory granules
;
Calcium
;
Parathyroid hormone storage and release
;
Hydrolysis
;
Trans Golgi network
;
Vacuolar bodies
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Natural Sciences in General
Notes:
Both prosecretory and storage granules are concomitantly formed at the trans Golgi network including the innermost Golgi cisterna. Prosecretory granules develop into small secretory granules that release their contents by exocytosis finely regulated by a complex mechanism for maintaining calcium homeostasis. In the rat parathyroid cells, storage granules are large secretory granules storing parathyroid hormone for an emergency supply. The hormone is rapidly discharged by exocytosis when serum calcium concentration is decreased. The granules are constantly produced even under conditions of low serum calcium concentration in the regions of 8 mg/dl. The granule content is constantly hydrolyzed when not discharged, leading to a decreased core and finally to the formation of vacuolar bodies. The fate of the vacuolar bodies is unknown. Hypercalcemic conditions accelerate hydrolysis. The threshold value of calcium concentration required for the release of storage granule contents is between 8.0 and 7.5 mg/dl and that of calcium concentration for accelerating degradation of storage granules is about 11.5 mg/dl. Sympathetic stimulation causes storage granules to be discharged regardless of hypercalcemia or hypocalcemia. Parasympathetic stimulation accelerates hydrolysis. The degradation of storage granules seems to be closely associated with an intracellular regulatory mechanism for parathyroid hormone secretion. © 1995 Wiley-Liss, Inc.
Additional Material:
18 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jemt.1070320209
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