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: Pharmacology
Which of the following statement is true about nitrates 
Select and explain. 
A. Acts by raising CGMP which causes dephosphorylation of MLCK, B. Metabolized by glutathione reductase, C. Used in achlasia cardia, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Nitrates acts by releasing nitric oxide which increases cGMP that cause dephosphorylation of myosin light chain kinase. These are preferential dilators of venules because glutathione reductase (enzyme that release NO from nitrates) is principally present at these sites. These agents are smooth muscle relaxants and can be used in colic and achlasia cardia Refer kDT 6/e p523