Cholinergic regulation of human proximal duodenal mucosal bicarbonate secretion.
Cephalic-vagal stimulation affects a number of upper gastrointestinal secretory and motility events. The purpose of this study was to examine the role of vagal-cholinergic regulation on human proximal duodenal mucosal HCO-3 secretion. The duodenal bulb was isolated between balloons and perfused with 154 mM NaCl, and HCO-3 secretion was measured. Although cholinergic stimulation with bethanechol (50 micrograms.kg-1.h-1 iv) produced systemic effects, resting HCO-3 secretion was unchanged. Cephalic-vagal stimulation, induced by sham feeding, significantly increased duodenal HCO-3 secretion from a basal of 177 +/- 17 to 240 +/- 19 mumols.cm-1.h-1 (P less than 0.02). The response to sham feeding was approximately 50% of the peak response to acid-stimulated HCO-3 output. Atropine (22 micrograms/kg iv) inhibited basal HCO-3 secretion significantly (79 +/- 5%). However, the net incremental increases in duodenal mucosal HCO-3 secretion in response to luminal acidification and vagal stimulation were unaltered by atropine pretreatment. Additionally, indomethacin (100 mg po) failed to modify the response to vagal-stimulated HCO-3 secretion. These findings indicate that basal human proximal duodenal mucosal HCO-3 secretion is maintained largely by resting cholinergic innervation and is stimulated by cephalic-vagal stimulation. Furthermore, since the incremental HCO-3 responses to cephalic-vagal stimulation and luminal acidification were unaltered by atropine pretreatment, each is likely mediated by noncholinergic mechanisms.
Department of Medicine, University of California Medical Center, San Diego 92103.
M A
MA
Ballesteros
J D
JD
Wolosin
D L
DL
Hogan
M A
MA
Koss
J I
JI
Isenberg
D000328:Adult; D001285:Atropine / Q000494:pharmacology; D018723:Bethanechol; D001626:Bethanechol Compounds / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism*; D001921:Brain / Q000502:physiology; D004386:Duodenum / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D008875:Middle Aged; D010277:Parasympathomimetics / Q000494:pharmacology*; D014630:Vagus Nerve / Q000502:physiology
D001626:Bethanechol Compounds; D001639:Bicarbonates; D010277:Parasympathomimetics; D018723:Bethanechol; D001285:Atropine