This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'The coronary blood flow is regulated by \nSelect and explain. \nA. Adenosine, B. Bradykinin, C. Prostaglandin, D. Increased aerial pCO2', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Coronary blood flow is regulated by Adenosine. Blood flow through the coronary system is regulated mostly by local aeriolar vasodilation in response to the nutritional needs of cardiac muscle. Increased local metabolism - decrease in O2 - breakdown of ATP to form adenosine - vasodilation - increased local coronary blood flow Ref: Guyton and hall 13th edition Pgno: 262,263', 'role': 'assistant'}]