Parathyroid Hormone Induction of Cyclooxygenase-2 Expression in Human Osteoblasts Depends on Both Cyclic AMP and Calcium-Dependent Pathways

Parathyroid Hormone Enhances Fluid Shear-Induced [Ca2+]i Signaling in Osteoblastic Cells Through Activation of Mechanosensitive and Voltage-Sensitive Ca2+ Channels

“…An increase in [Ca 2+ ] i also is involved in PTH‐stimulated production of the inducible prostaglandin synthesis enzyme, cyclo‐oxygenase‐2. ( 18 )…”

“…An increase in [Ca 2ϩ ] i also is involved in PTH-stimulated production of the inducible prostaglandin synthesis enzyme, cyclooxygenase-2. (18) Duncan et al (8,19,20) have characterized a mechanosensitive cation-selective channel (MSCC) in osteoblasts that may account for [Ca 2ϩ ] i transients observed in osteoblasts. Patch clamp and [Ca 2ϩ ] i imaging studies indicate that this channel is activated by membrane deformation induced by fluid shear, (5) hypotonic swelling, (8) and strain.…”

Parathyroid Hormone Enhances Mechanically Induced Bone Formation, Possibly Involving L-Type Voltage-Sensitive Calcium Channels

“…An early response to both stimuli is a rapid increase in intracellular calcium ([Ca 2ϩ ] i ) that is dependent on both extracellular Ca 2ϩ entry and [Ca 2ϩ ] i release (8 -10). The early increase in [Ca 2ϩ ] i has been linked to increased production of nitric oxide and prostaglandins in osteoblasts (11,12) and up-regulation of some skeletal growth factors, including IGF-I and TGF␤ (13,14). Both nitric oxide and prostaglandins have been shown to mediate loadinduced bone formation in vivo (15)(16)(17).…”