This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autacoids, Subject name: Pharmacology
[{'content': 'Bosentan is a/an: \nSelect and explain. \nA. Serotonin uptake, B. Endothelin receptor antagonist, C. Leukotriene modifier, D. Phosphodiestease inhibitor', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Endothelin receptors are of 2 types 1.ET A - in smooth muscles 2.ET B - in vascular endothelial cells BOSETAN , macicentan: endothelin receptor antagonists used for the treatment of pulmonary hypeension Ref: KD Tripathi 8th ed', 'role': 'assistant'}]