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: Pathology
[{'content': 'All of the following about prostaglandins are TRUE, EXCEPT: \nSelect and explain. \nA. Synthesised from arachidonic acid, B. First isolated from semen, C. Prostaglandins contain a cyclopentane ring, D. PGE1 and PGE2 increase in bronchial asthma', 'role': 'user'}, {'content': "Answer: D \nExplanation: Prostacyclin is produced by endothelial cells and thromboxane A2 by platelets from their common precursor, arachidonic acid. Prostaglandins are a series of 20-carbon unsaturated fatty acids containing a cyclopentane ring. It was first isolated from semen but are synthesized in most and possibly in all organs in the body. Respiratory smooth muscle is relaxed by PGE2 and PGI2 and contracted by PGD2, TXA2, and PGF2a. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 1. General Principles & Energy Production in Medical Physiology. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.", 'role': 'assistant'}]