<prompt> Which of the following statements is true about nitrates?Acts by raising cGMP which causes dephosphorylation of MLCKMetabolized by glutathione reductaseUsed in achalasia cardiaAll of the above  <response>: Ans. D All of the aboveRef: KDT 8the p586, 587, 590Nitrates act by releasing NO which increases cGMP that cause dephosphorylation of myosin light chain kinase. These are preferential dilator of venules because glutathione reductase enzyme that releases NO from nitrates is principally present at these sites. These agents are smooth muscle relaxants and can be used in colics and in achlasia cardia. 