Box 5.11Control of PTH secretion

Image ch5fb11.jpg

The circulating concentration of Ca2+ is detected by a unique G-protein-linked calcium receptor (CaR) on the cell surface of the chief cells. When the Ca2+ concentration is high the α-subunit of the G-protein preferentially stimulates phospholipase C (PLC) with the hydrolysis of phosphatidyl inositol 4, 5-bisphosphate (PIP2) IP2 to diacylglycerol (DAG) and inositol 1, 4, 5-trisphosphate (IP3). Adenylate cyclase (AC)-induced cAMP generation is inhibited and so is PTH secretion. The reverse occurs when the Ca2 concentration is low and thus PTH secretion is stimulated. When calcium concentrations are within their normal limits the two second messenger pathways are balanced and basal secretions of PTH are maintained.

From: Chapter 5, The parathyroid glands and vitamin D

Cover of Endocrinology
Endocrinology: An Integrated Approach.
Nussey S, Whitehead S.
Copyright © 2001, BIOS Scientific Publishers Limited.

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