Bile acid active and passive ileal transport in the rabbit: effect of luminal stirring.
The intestinal absorption of bile acids (BA) with different chemical structure has been evaluated in the rabbit, after intestinal infusion of different concentrations (0.25-30 mM) of BA, by mesenteric blood sampling. Cholic (CA), chenodeoxycholic (CDCA), ursodeoxycholic (UDCA) acid, free and taurine (T-) conjugated, together with glycocholic (GCA) acid and deoxycholic acid (DCA) were studied. The apparent uptake parameters were calculated. All conjugated BA showed active transport (T max, nmol min-1 cm-1 int.), with Tmax values in the following order: TCA > TUDCA > TCDCA; unconjugated BA showed passive uptake, with values in the following order: DCA > CDCA > UDCA > CA. GCA and CA showed both passive uptake and active transport. For all BA studied the % uptake in the ileal segment considered was less than 10%, BA uptake being thus limited by transport and/or diffusion kinetics, rather than by flow velocity. The liquid resistance to BA radial diffusion inside the lumen was evaluated, and the infusate-to-blood uptake parameters corrected for it, in order to get the uptake parameters from the epithelium-to-liquid interface to mesenteric blood: the apparent Km decreased, passive uptake coefficient increased, while Tmax was unchanged. The passive component of the uptake, corrected for the luminal resistance, correlated with the BA hydrophobicity (r = 0.963; P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Aldini
R
R
Istituto di Scienze Chimiche, Università di Bologna, Italy.
Roda
A
A
Lenzi
P L
PL
Ussia
G
G
Vaccari
M C
MC
Mazzella
G
G
Festi
D
D
Bazzoli
F
F
Galletti
G
G
Casanova
S
S
D000818:Animals; D001647:Bile Acids and Salts / Q000737:chemistry / Q000378:metabolism*; D001693:Biological Transport, Active; D004058:Diffusion; D007082:Ileum / Q000378:metabolism*; D007408:Intestinal Absorption; D007700:Kinetics; D008297:Male; D011817:Rabbits
D001647:Bile Acids and Salts