Mechanism of action of intracisternal apolipoprotein A-IV in inhibiting gastric acid secretion in rats.
BACKGROUND & AIMS: We recently showed that intracisternal injection of apolipoprotein A-IV (apo A-IV), a protein produced by the small intestine in response to fat, inhibits gastric acid secretion. The aim of this study was to investigate the mechanism of acid inhibition by central apo A-IV. METHODS: Gastric acid secretion was determined in pylorus-ligated conscious rats. The effect of intracisternal injection of apo A-IV on gastric acid secretion stimulated by pentagastrin, bethanechol, or intracisternal thyrotropin-releasing hormone (central vagal stimulant) was examined. The effects of vagotomy, indomethacin, and adrenergic blockers on the acid inhibition of apo A-IV were examined to investigate the role of the vagal system, prostaglandin pathways, and adrenergic system. RESULTS: Intracisternal apo A-IV significantly inhibited pentagastrin-, bethanechol-, and thyrotropin-releasing hormone-stimulated gastric acid secretion in a similar fashion. Inhibition of pentagastrin-stimulated acid secretion by apo A-IV still occurred even in vagotomized rats. Yohimbine but not indomethacin or propranolol eliminated apo A-IV--induced inhibition of acid. CONCLUSIONS: Intracisternal apo A-IV inhibits gastric acid secretion through alpha 2-adrenergic receptors. The vagal pathway and the prostaglandin system are not involved in apo A-IV--induced acid inhibition.
Okumura, T; Fukagawa, K; Tso, P; Taylor, IL; Pappas, TN
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