Gastric secretion in the rat following histidine loading

Amino Acid Decarboxylase Enzymes – Vital or Irrelevant to Gastric Secretion?

“…Hakanson and Liedberg (42) showed that hourly injections of pentagastrin led to progressive increases in gastric enzyme activity but did not cause progressive, or even maintained, depletion of gastric tissue histamine content. On the other hand, the pentagastrin-induced activation of histidine decarboxylase is prevented by loading with histidine or histamine in large amounts (9,67,146). However, this argument seems to be largely irrele vant to gastric secretion stimulated by gastrin-like secretagogues (69,71) since secretin inhibits such secretion (73,150) without blocking the increased enzyme levels (19) or the release of gastric histamine (9); whilst histidine loading pre vents the enzyme induction but not the gastric secretion (146).…”

“…On the other hand, the pentagastrin-induced activation of histidine decarboxylase is prevented by loading with histidine or histamine in large amounts (9,67,146). However, this argument seems to be largely irrele vant to gastric secretion stimulated by gastrin-like secretagogues (69,71) since secretin inhibits such secretion (73,150) without blocking the increased enzyme levels (19) or the release of gastric histamine (9); whilst histidine loading pre vents the enzyme induction but not the gastric secretion (146). Further, antrec tomy abolishes the ability of insulin to stimulate gastric histidine decarboxylase and gastric histamine release without abolishing its ability to stimulate gastric secretion in the gastric fistula rat (40).…”

“…Such a mechanism may sometimes apply, for example, when histamine or histidine is administered in excess (9,67,146), but it can be overridden (26,27,42,69,155).…”