Which of the following is not the action of calcitriol?
Calcitriol increases the intestinal absorption of calcium and phosphate. 
In the osteoblasts of bone,  calcitriol stimulates calcium uptake for deposition as calcium phosphate, Thus calcitriol is essential  for bone formation. 
Calcitriol is also involved in minimizing the excretion of calcium and phosphate through the kidney, by decreasing their excretion' and enhancing reabsorption.  
Calcitriol action is similar to steroid hormones. lt binds to a receptor in the cytosol and the complex  acts on DNA to stimulate the synthesis of calcium binding protein.

Reference: Satyanarayana- Biochemistry, 3rd edition, pg-125
Calcitriol increases the intestinal absorption of calcium
Calcitriol stimulates  calcium uptake  for deposition  as calcium phosphate in the osteoblasts  of bone
Calcitriol increases the excretion of calcium and phosphate  through the kidney
Calcitriol  action  is  similar  to  steroid hormones