Bicarbonate transport by rabbit duodenum in vitro: effect of vasoactive intestinal polypeptide, prostaglandin E2, and cyclic adenosine monophosphate.
BACKGROUND
Duodenal surface cells secrete bicarbonate that provides a barrier against injury. The current experiments were performed to identify duodenal bicarbonate regulatory and transport pathways.


METHODS
Rabbit proximal duodenal mucosa were mounted in chambers under short-circuited conditions. Bicarbonate transport, short-circuit current (Isc), and potential difference (PD) were quantitated in response to prostaglandin E2 (PGE2), vasoactive intestinal polypeptide (VIP), and dibutyryl cyclic adenosine monophosphate (db-cAMP). Anoxia (N2), 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and Cl(-)-free solutions, ouabain, and Na-free solutions were also studied, as was the effect of VIP and PGE2 on duodenocyte cAMP.


RESULTS
PGE2, VIP, db-cAMP, and theophylline significantly increased bicarbonate secretion, Isc, and PD. Ouabain, Na(+)-free bathing solutions, and anoxia (N2) inhibited the responses. DIDS and Cl(-)-free solutions abolished the PGE2-induced response, reduced the response to VIP by about 50%, and had no effect on the response to db-cAMP. After PGE2 and VIP, cAMP concentration increased, yet was likely independent of bicarbonate secretion.


CONCLUSIONS
Mammalian duodenal HCO3- transport requires Na+, Na+/K(+)-adenosine triphosphatase and O2-dependent metabolic pathways and is stimulated by PGE2, VIP, and cAMP, acting by distinct pathways.
Department of Medicine, UCSD Medical Center.
B
B
Yao
D L
DL
Hogan
K
K
Bukhave
M A
MA
Koss
J I
JI
Isenberg
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D003994:Bucladesine / Q000494:pharmacology*; D002712:Chlorides / Q000378:metabolism; D000242:Cyclic AMP / Q000032:analysis; D015232:Dinoprostone / Q000494:pharmacology*; D004386:Duodenum / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000502:physiology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D001639:Bicarbonates; D002712:Chlorides; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D014660:Vasoactive Intestinal Peptide; D010042:Ouabain; D003994:Bucladesine; D012964:Sodium; D000242:Cyclic AMP; D015232:Dinoprostone; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid