[Parathyroid hormone : its anabolic action on bone].
PTH actions on bone are exerted through multiple pathways from G-proteins coupled to a receptor PTH1R that is expressed on osteoblastic lineage cells. Physiological action of PTH may be through increased expression of RANKL, resulting in increased bone resorption and Ca( + + ) release from bone matrix by osteoclasts. Bone anabolic action of PTH by intermittent treatment is explained by ( I ) proliferation of osteogenic precursor cells, ( II ) differentiation of osteoblasts, ( III ) inhibition of apoptosis in osteoblastic cells, and ( IV ) inhibition of canonical Wnt inhibitor secretion from osteocytes. Two of these mechanisms ( II and III ) could be secondary to increased osteoclastogenesis after induction of RANKL in osteoblastic cells. Mechanisms involved in ( I ) might be controversial depending on cellular status including differentiation stages and cell density, and thus need to be clarified by further studies.
Department of Molecular Pharmacology, Tokyo Medical and Dental University, Japan.
Yoichi
Y
Ezura
Masaki
M
Noda
D000818:Animals; D016723:Bone Remodeling / Q000502:physiology; D001862:Bone Resorption / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism*; D006801:Humans; D010006:Osteoblasts / Q000378:metabolism; D010281:Parathyroid Hormone / Q000378:metabolism*; D053245:RANK Ligand / Q000378:metabolism
D010281:Parathyroid Hormone; D053245:RANK Ligand