bm
Forum Elite
Topics: 37
Posts: 421
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in page 436 of kaplan2002 physiology, it says there on the note on bone cells that the PTH receptors are actually on the OSTEOBLASTS. i'm quite confused since the main function of PTH is to raise free calcium. It does this thru the fast and slow mechanisms, the slow being the increase in the formation and activity of OSTEOCLASTS.
is this a typo or are the PTH receptors really on osteoblasts? how do you account for its action on the osteoclasts?
please help...
thanks
may
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| Idiopathic
Forum Guru
Topics: 19
Posts: 641
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Yes they are. It has only recently been discovered that there are PTH receptors on osteoclasts.
Primary mechanism = inhibition of osteoblast activity
Secondary mechanism = (could be) direct stimulation of osteoclast activity
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| Sakaki-
Forum Senior
Topics: 1
Posts: 238
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The PTH binds to its receptor on the osteoblast, causing upregulation of RANKL, a receptor activator on osteoblast cells (RANKL stands for receptor activator of NF-kB ligand). PTH also decreases the production of osteoprotegerin, which normally binds this RANKL on the osteoblasts and "covers it".
The increased number of RANKL (and exposed now) binds to RANK on the osteoclast precursor, stimulating its differentiation into a mature, functional osteoclast, with a resultant increase in bone resorption.
So PTH indirectly activates the osteoclasts.
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| mani
Forum Guru
Topics: 104
Posts: 1,403
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receptors of PTH on osteoblasts cause increased pumping of Ca out of matrix in to blood
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