This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Which one one of the following acts to increase the release of Ca2+ from endoplasmic reticulum: 
Select and explain. 
A. Inositol triphosphate, B. 4,Parathyroid hormone, C. 1, 25-dihydroxy cholecalciferol, D. Diacyglycerol
A: Inositol triphosphate
Answer: A: Inositol triphosphate 
Explanation: A i.e. Inositol triphosphate Inositol triphosphate diffuses to the endoplasmic reticulum, where it triggers the release of calcium into cytoplasm. Inositol triphosphate and diacylglycerol (DAG) both of which are second messengers, are associated with Gq subset of G protein mediated receptors.