Circulating immunoreactive somatostatin in gastrointestinal diseases. Decrease after vagotomy and enhancement in active ulcerative colitis, irritable bowel syndrome, and duodenal ulcer.

The main source of circulating immunoreactive somatostatin (IRS) seems to be the gastrointestinal tract. We therefore investigated plasma IRS in patients with various gastrointestinal diseases. Mean basal IRS oscillated between 46 and 73 pg/ml. A postprandial rise was observed in all patients and age-matched controls. However, the increment was significantly higher in patients with duodenal ulcer (159 +/- 20 pg/ml), active ulcerative colitis (176 +/- 17 pg/ml), and irritable bowel syndrome (194.4 +/- 20.4 pg/ml). Patients with duodenal ulcers who underwent vagotomy showed a decreased postprandial increment (107 +/- 10 pg/ml) when compared with active duodenal ulcer patients. No difference was demonstrable between controls and individuals with gastric ulcer, and patients with inactive ulcerative colitis. These results suggest that vagal innervation plays a role in postprandial IRS stimulation, whereas gastric hyperacidity, acute lesions of the colonic mucosa, and hypermotility of the gastrointestinal tract are associated with an exaggerated postprandial IRS response. Since somatostatin is known to influence many gastrointestinal functions, these variations in circulating IRS concentrations may be of pathophysiologic importance.