???? Mechanism of Action ????
???? Vitamin D :-
????1. Calcitriol enhances absorption of calcium and phosphate from intestine.
This is brought about by synthesis of calcium channels and carrier protein for Calcium called Calcium Binding Protein (CaBP) or Calbindin. Vitamin D shows it’s action through Cytoplasmic receptor (VDR) .
????2. Calcitriol enhances resorption of calcium and phosphate from bone by promoting recruitment and differentiation of osteoclasts precursors in the bone remodeling units, but mature osteoclasts lack the VDR i.e. Vitamin D receptor.
????3.Caltriol enhances tubular reabsorption of Calcium and phosphate in the kidney, but action is less marked than PTH.
????4. Other actions :- Lymphokine production , proliferation and differentiation of epidermal cells, neuronal and skeletal muscle function have also been demonstrated.