I am confused about my teacher's notes. "Acid secretion is stimulated by ACh, gastrin and histamine. Histamine stimulates adenylate cyclase which increases cAMP production."

When I looked this up apparently gastrin decreases AC (adenylate cyclase) production. If histamine and gastrin both stimulate acid secretion why does one increase and the other decrease AC?

Also in her notes the acid secretion inhibitors are acid, protein, fat as they cause the secretion of CCK and secretin and these stimulate AC. But I thought AC stimulated acid secretion not inhibited it?

Thank you.

  • $\begingroup$ Can you share your reference for your reading about gastrin decreasing adenylate cyclase? In parietal cells, gastrin acts through a separate second messenger system, $IP_3$ and $Ca^{++}$, where histamine acts through cAMP. $\endgroup$ – De Novo Jul 16 '18 at 18:23
  • $\begingroup$ That makes more sense. Does the CCK only use AC to stimulate acid secretion then? I think CCKb receptor is used to stimulate acid secretion and inhibit it by the CCKa receptor? It says this in my teachers notes: "CCK and secretin both act to stimulate adenylate cyclase (pro-secretory): hence, actions on acid secretion are indirect." but why are CCK and secretin in the inhibitory section of gastric secretion. $\endgroup$ – marley Jul 16 '18 at 19:34

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