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: Physiology
[{'content': 'Relaxation of mesangial cells of the kidney is brought about by \nSelect and explain. \nA. cAMP, B. Endothelin, C. PGF2, D. Vasopressin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Substances causing relaxation of mesangial cells\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 ANP\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Dopamine\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 PGE2\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 cAMP\nSubstances causing contraction of mesangial cells\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Endothelin\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Vasopressin\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 PGF2\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Angiotensin II\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Norepinephrine\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 PAF\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 PDGF\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Thromboxane A2\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Leukotrienes C4, D4\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Histamine', 'role': 'assistant'}]