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Old 10-04-2012
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Drug pharmacological blockade of histamine H2 receptors in the gastric mucosa

Which of the following is true regarding the pharmacological blockade of histamine H2 receptors in the gastric mucosa?
A. It inhibits both gastrin-and Ach-mediated secretion of acid
B. It inhibits gastrin-induced but not meal-stimulated secretion of acid
C. It has no effect on either gastrin-induced or meal-stimulated secretion of acid
D. It prevents activation of adenyl cyclase by gastrin
E. It causes an increase in potassium transport by gastric parietal cells

guys,plz answer with a bit explanation
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Old 10-04-2012
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Default D. It prevents activation of adenyl cyclase by gastrin

confusing options
What i know is H2 blockers decreases H-ion secretion which leads to decrease in H+-K+ ATPase pump
but if i remember correctly it also inhibit cAMP activity but not sure would it have effect on gastrin or not.
So, Not sure but my guess would be D
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Will go with A.
What's the answer?
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ya mostly D
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Default The answer is A

Histamine receptors antagonists inhibit both gastrin and vagal mediated secretion of acid. Secretion of acid by gastric parietal cells involves stimulation of adenyl cyclase and cyclic AMP-mediated stimulation of the active transport of chloride and potassium-hydrogen ion exchange. Neither gastrin nor vagal stimulation activates adenyl cyclase directly; both depend on concomitant release of histamine and histamine-induced activation of adenyl cyclase.

(guys this is from Pretest self assessment, but i think this answer doesn't correlate with what is mentioned in BRS physiology. Lemme post that figure here)
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