All small GTPases of the Ras superfamily, Cdc42, Rac, and Rho act as molecular switches, inactive in the GDP-bound state and active in the GTP-bound state.

TLS Online TPP Program

#Id: 1224

#Unit 7. System Physiology – Animal

Two osteoblast proteins responsible for osteoclast maturation: 

1. Receptor activator for nuclear factor κ-B ligand  

2. Macrophage colony-stimulating factor

TLS Online TPP Program

#Id: 1225

#Unit 7. System Physiology – Animal

Osteoblasts also produce osteoprotegerin, a cytokine that inhibits bone resorption. ate osteoclast activity and bone resorption.

TLS Online TPP Program

#Id: 1226

#Unit 7. System Physiology – Animal

Vitamin D and PTH appear to stimulate production of mature osteoclasts through the dual action:

 1. Inhibiting OPG production

2. Stimulating RANKL formation

TLS Online TPP Program

#Id: 1227

#Unit 7. System Physiology – Animal

Glucocorticoids promote osteoclast activity and bone resorption by :

1. Increasing RANKL production 

2. Decreasing formation of OPG

TLS Online TPP Program

#Id: 1228

#Unit 7. System Physiology – Animal

Estrogen stimulates OPG production

TLS Online TPP Program

#Id: 1229

#Unit 7. System Physiology – Animal

PTH actions on the kidney:

1.  Inhibits phosphate reabsorption

2.  Stimulates Ca2+ reabsorption