Utility of endoscopic biopsy samples to quantitate human duodenal ion transport

Duodenal mucosal bicarbonate secretion (DMBS) prevents acid-peptic damage a nd facilitates nutrient absorption. DMBS is diminished in patients with duo denal ulcers and is normalized after Helicobacter pylori eradication. The m easurement of DMBS in human patients in vivo requires intubation with a mul ti-lumen balloon tube and permits limited testing with putative agonists an d antagonists. Our purpose was to develop a means to investigate transport events in human duodenal biopsy samples in vitro. After validation studies in a modified mini-Ussing chamber were performed, duodenal transport events were examined in proximal endoscopic biopsy samples from normal volunteers (n = 17), Tissues were mounted in modified mini-Ussing chambers (volume 2. 5 ml, surface area 3.8 mm(2)). Short circuit current (I-sc), potential diff erence (PD), and bicarbonate secretion were determined under basal conditio ns and after stimulation with graded doses of prostaglandin E-2 (PGE(2))(10 (-8) to 10(-4) mol/L) and dibutyryl cAMP (db-cAMP)(10(-4) to 10(-2) mol/L). Duodenal tissues remained viable for at least 2 hours and exhibited stable basal HCO3- secretion and electrical parameters. Stimulation with PGE(2) a nd db-cAMP resulted in dose-related increases in both I-sc and HCO3- secret ion (P <.05) that were abolished by ouabain and anoxia. It is concluded (1) that human duodenal bulb biopsy samples maintain their inherent transport function in mini-Ussing chambers and (2) that by using this novel method it will be possible to define the transport events that modulate human duoden al secretion, in particular bicarbonate secretion, in both health and disea se.