2.5 Extracellular calcium and phosphate homeostasis Flashcards
How is extracellular calcium stored and when can it be filtered?
It can either be bound (albumin and globulin) or free. It is the free form that can be filtered
What is the transporters involved in Ca outflow?
CA-ATPase and Na/Ca exchanger
Describe the transcellular pathway of Ca
Ca comes in thrugh luminal channel and binds to Calbindin (binding protein). This is transported through the cell and will leave as unbound Ca via the CA-ATPase and NA/Ca exchanger
What can speed up the process of resorption of Ca?
Calcitriol - increases protein expression of calbindin
Where is Ca excreted?
Kidney
What is the rate limiting factor in Ca resortion?
The Na/Ca exchanger and CaATPase
What is the short and long term regulators of calcium?
Short: pH
Long: Ca sensing on cell membrane and hormonal feedback loops
What happens to Ca in alkalosis and acidosis?
Increases in acidosis, decreases in alkalosis
What is the role of calcium sensor proteins and give an example
They bind to a host of adaptor proteins leading to transduction pathways and regulated processes such as synaptic plasticity, memory formation, gene expression
Neuronal calcium sensor-1
What is the role of calcitonin?
Released in proportion to Ca and acts to inhibit osteoclast activity in bone, converts active vitamin D into inactive in the kidney causing decreased Ca absorption
What effect does PTH have on Ca and phosphate?
increase calcium, decrease phosphate
what effect does calcitriol have on Ca and phosphate?
Increase clacium and increase phosphate (increased uptake and renal reabsorption)
What effect does calcitonin have on Ca and phosphate?
Decreases both
