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
[{'content': 'Increase in cytosolic calcium from intracellular storage, during smooth muscle contraction, is/are due to - \nSelect and explain. \nA. cAMP, B. cGMP, C. cCMP, D. IP3-DAG', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The release of Ca++ from intracellular source, that is sarcoplasmic reticulum, is by IP3-DAG second messenger system, whereas the pumping of Ca++ from extracellular space to cytosol is by Ca++ channels. \nIP3 when bound to its receptors on sarcoplasmic reticulum, causes the release of calcium into sarcoplasm.', 'role': 'assistant'}]