A basic in vitro study on pepsinogen secretion in the bullfrog.

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The in vitro release of pepsinogen in bullfrogs was studied using our new system of four matched chambers. The lower esophageal mucosa of this species has been characterized to have special peptic glands without acid-secreting cells. The excised mucosa was placed in the fourth chamber which preserves the mucosal polarity with an exposed surface area of 1cm2/segment. Histamine, an acid secretagogue, demonstrated no effect on pepsinogen secretion, which was stimulated moderately by pentagastrin and strongly by bethanechol (Bch). Bch concentrations of 0.5 to 50μM were found in our system to result in concentration-dependent stimulation of pepsinogen secretion (Km 1.79μM, Vmax 30.62μg/mg•protein/hr). Atropine sulfate antagonistically inhibited the Bch-stimulated secretion of pepsinogen (pA2 9.30). Isobutylmethylxanthine, an inhibitor of the phosphodiesterase activity, and db-cAMP released pepsinogen significantly. The release of pepsinogen occurred in the presence of various concentrations of extracellular Ca2+. The pepsinogen release was reduced especially in the medium containing EGTA or containing no Ca2+. The reduction of pepsinogen release also occurred by Bch stimulation. CCCP, an inhibitor of tissue respiration, significantly inhibited the Bch-stimulated pepsinogen secretion.The cholinergic drug, Bch, induced strongest stimulation of pepsinogen secretion from the esophageal mucosa, and cAMP and Ca2+ were presumed to be associated with the process of pepsinogen release.It was concluded that the in vitro chamber system developed by us is advantageous for observation purely and singly of pepsinogen secretion without being subjected to the effect of acid secretion.
財団法人日本消化器病学会の論文

A basic in vitro study on pepsinogen secretion in the bullfrog.

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