Duodenal osmolality drives gallbladder emptying in humans.

The effect of duodenal osmoreceptor stimulation on gallbladder motility was evaluated in 18 normal subjects during intraduodenal infusion of 280, 560 and 840 mosm/liters NaCl solutions. Gallbladder emptying was found to be dose-dependent between 560 and 840 mosm/liter (P less than 0.01 vs basal volume). The effect of duodenal infusion of hypertonic saline on gallbladder emptying was prevented by atropine and partially antagonized by naloxone, indicating that cholinergic and endorphinergic pathways may be involved in regulating this reflex. Since proglumide, a cholecystokinin (CCK) antagonist, did not affect gallbladder emptying induced by hypertonic saline, it seems likely that CCK is not released by increasing duodenal osmolality. A significant reduction in gallbladder volume was obtained when hyperosmolar saline was delivered into the duodenum, whereas no emptying was seen when infused into the gastric antrum or the jejunum, suggesting that osmoreceptors that activate gallbladder emptying are located only in the duodenum. Additionally, all subjects manifested central symptoms (nausea or vomiting) during duodenal infusion of hypertonic saline, suggesting that central mechanisms might be activated by a change in duodenal osmolality. Our data indicate that the osmolality of duodenal contents might regulate gallbladder motility by neural atropine- and naloxone-sensitive pathways.