pH Threshold for Release of Secretin in Normal Subjects and in Patients with Duodenal Ulcer and Patients with Chronic Pancreatitis

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Abstract
In 7 normal controls (C), 9 duodenal ulcer patients (DU), and 4 patients with chronic pancreatitis (CP), the duodenum, was perfused with isotonic citrate buffers with pH 4, 3, 2, and 1. The buffers were infused at a rate of 52 ml per min for 20 min, with a resting period of 20 min between infusions. In this way a very stable and reproducible duodenal acidity was obtained. With the use of 51Cr-EDTA as a volume marker for the citrate buffers, the disappearance rate of acid from the duodenum was calculated from the difference in pH between the infused buffer and the aspirated duodenal contents. Venous blood samples were taken every 10 min for secretin determination (radioimmunoassay). The mean plasma secretin concentration was below 3 pmol × 1-1 at pH 4, and no change was observed at pH 3. Perfusion at pH 2 caused a small but statistically significant (p1, and it rose to values around 12 pmol × 1-1 at pH 1. No significant difference was found between the 3 groups. The disappearance rate of acid from the duodenum was the same for the controls and the patients at pH 4 (1.2 mEq/15 min) and pH 3 (2.0 mEq/15 min). No difference was found between C and DU patients at pH 2 (5.0 mEq/15 min) or at pH 1(11.0 mEq/15 min), while the CP patients were significantly lower (pH2:2.1 mEq/15 min, pH 1:4.5 mEq/15 min). The results of this study demonstrate that the pH threshold for secretin release is between pH 2 and 3, with no difference between normal man and patients with duodenal ulcer or chronic pancreatitis.