An investigator is studying the effect of a new drug on gastric mucosa cells. She finds that under physiologic conditions, the new drug acts as a competitive antagonist of a G-protein coupled receptor that is located on the cell membrane of parietal cells. Activation of this type of receptor increases the intracellular concentration of cyclic adenosine monophosphate. The mechanism of action of the new drug is most similar to that of which of the following?

Question

Quizplus · Accepted Answer

Eductional Objective: Cimetidine is a competitive antagonist of histamine-2 (H2) receptors, which are found on parietal cells and are Gs-protein coupled receptors. Activation of these receptors would increase adenylyl cyclase activity, which leads to increased cyclic adenosine monophosphate (cAMP) levels. cAMP activates protein kinase A, which, in turn, phosphorylates and activates the proton pump (H+/K+ ATPase). H2 receptor antagonists would, therefore, decrease cAMP levels in parietal cells and decrease gastric acid secretion. The mechanism of action of the drug being studied by the investigator is most similar to this class of drugs.

An Investigator Is Studying the Effect of a New Drug