Intestinal absorption of bile acids in the rabbit: different transport rates in jejunum and ileum.
OBJECTIVE
A direct comparison of jejunal and ileal absorption rates of bile acids has not been reported. The aim of this study was to compare the relative transport rates of different bile acids in the jejunum and ileum.


METHODS
Jejunal and ileal rabbit intestinal segments were separately perfused with bile acid solutions, and dose-response curves were obtained for taurocholate, ursodeoxycholate, chenodeoxycholate, deoxycholate, and their glycoconjugates. Membrane fluidity and bile acid transport were assessed in brush border membrane vesicles.


RESULTS
Taurocholate showed active transport in the ileum and no transport in the jejunum. Unconjugated bile acids showed passive diffusion in the two tracts, whereas glycoconjugated bile acids showed both components of transport in the ileum and passive diffusion in the jejunum (lower in the latter). A higher membrane fluidity and lower cholesterol-to-phospholipid ratio were found in the jejunum. Ursodeoxycholate reduced bile acid uptake into membrane vesicles from both ileum and jejunum.


CONCLUSIONS
Active transport is limited to the ileum. Passive diffusion is higher through a less fluid membrane with a higher cholesterol-to-phospholipid ratio in the ileum than in the jejunum. Ursodeoxycholate inhibition may be at the level of a facilitated, sodium-independent diffusion in the jejunum.
Aldini
R
R
Istituto di Scienze Chimiche, Università di Bologna, Italy.
Montagnani
M
M
Roda
A
A
Hrelia
S
S
Biagi
P L
PL
Roda
E
E
D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism*; D001693:Biological Transport, Active; D002635:Chenodeoxycholic Acid / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D003840:Deoxycholic Acid / Q000378:metabolism; D004058:Diffusion; D007082:Ileum / Q000378:metabolism*; D007408:Intestinal Absorption; D007583:Jejunum / Q000378:metabolism*; D008297:Male; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D011817:Rabbits; D013656:Taurocholic Acid / Q000378:metabolism; D014580:Ursodeoxycholic Acid / Q000378:metabolism / Q000502:physiology
D001647:Bile Acids and Salts; D008563:Membrane Lipids; D010743:Phospholipids; D003840:Deoxycholic Acid; D002635:Chenodeoxycholic Acid; D013656:Taurocholic Acid; D014580:Ursodeoxycholic Acid; D002784:Cholesterol