This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
[{'content': 'Pulmonary vasoconstriction is caused by all except \nSelect and explain. \nA. Hypoxia, B. Hypercarbia, C. Prostocyclin, D. Thromboxane A2', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Prostacyclin is produced by endothelial cells and thromboxane A2 by platelets from their common precursor arachidonic acid the cyclooxygenase pathway. Thromboxane A2 promotes platelet aggregation and vasoconstriction, whereas prostacyclin inhibits platelet aggregation and promotes vasodilation.Ref: Ganong review of medical physiology 23rd edition Page no: 563', 'role': 'assistant'}]