This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Biochemistry
[{'content': 'Which of the following substances acts to increase the release of Ca2+ from endoplasmic reticulum? \nSelect and explain. \nA. Inositol triphosphate, B. Parathyroid hormone, C. 1,25 dihydroxy cholecalciferol, D. Diacylglycerol', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. Inositol triphosphateInositol triphosphate (IP3 ) and diacylglycerol (DAG) are second messengers for G protein coupled receptors. IP3 stimulates release of calcium from endoplasmic reticulum. DAG activates protein kinase C.', 'role': 'assistant'}]