Thyrotropin-releasing hormone immunoreactivity in the gastrointestinal tract of man.

TRH inhibits gastric secretion, gastric motility, and pancreatic enzyme secretion in man. We measured TRH immunoreactivity (TRH-IR) in mucosal and transmural biopsies from different parts of the stomach, pylorus, duodenum, and pancreas in patients undergoing surgery or gastroscopy. TRH-IR was found in pancreas (range, 1.64-3.27 pg TRH/mg protein) and in mucosa of the fundus (13.3 +/- 2.0 pg TRH/mg protein), antrum (22.5 +/- 4.5 pg TRH/mg protein), and duodenum (35.5 +/- 6.4 mg TRH/mg protein). Low levels of TRH-IR were found in transmural biopsies from fundus, antrum, and pylorus (range, 0.45-0.87 pg TRH/mg protein). Chromatography of gastrointestinal tissue extracts on a cation exchange column resulted in two different TRH-IR peaks, one eluted at pH 3.5 and the other eluted at pH 7.4. The peak at pH 7.4 corresponded to synthetic TRH. The presence and the action of TRH in human gut indicate a physiological role of TRH in the gastrointestinal tract in man.