Intestinal Bile Acid Transport Research Articles

Modified bile acids as carriers for peptides and drugs

For the development of future drugs two aspects are of major importance, a site-specific drug action without adverse side-effects and a preferably oral applicability. The liver has a central role in drug action and many disorders are unique to the liver demanding a liver-specific drug action. In oral drug therapy the small intestine is often the limiting barrier of drug absorption. Bile acids are natural substrates undergoing an enterohepatic circulation involving the liver and the small intestine. This organotropism of bile acids is achieved by specific Na+-dependent transport systems in the plasma membrane of hepatocytes and ileocytes. Di- and tripeptides as well as orally active α-amino-β-lactam antibiotics are intestinally absorbed by a H+/oligopeptide cotransport system of high transport capacity. We, therefore, investigated whether the hepatic and the intestinal bile acid transport systems as well as the intestinal H+/oligopeptide transporter can be used in drug therapy to improve the membrane permeability and intestinal absorption of peptide drugs, to target a drug to the liver and the biliary system and to obtain liver-specific drugs. For this, modified bile acids with linkers of varying structure, length, position and stereochemistry at the steroid nucleus were synthesized and covalently linked to drugs or peptides or alternatively bile acid structural elements were introduced into drugs. To investigate the H+/oligopeptide transporter as a putative peptide delivery system, peptides were covalently attached to the 3′-position of the tripeptide-analogue d-cephalexin. The interaction of these bile acid and cephalexin conjugates with the hepatic and intestinal bile acid and peptide transport systems as well as their pharmacokinetic and pharmacodynamic behaviour was investigated by transport measurements and photoaffinity labeling techniques using membrane vesicles, isolated hepatocytes and in vivo models.

Increases in plasma motilin follow each episode of gallbladder emptying during the interdigestive period, and changes in serum bile acid concentration correlate to plasma motilin.

The relationship between each single period of gallbladder emptying during the migrating motor complex (MMC) cycle and changes in concentration of plasma motilin and serum bile acids is unknown. The variations in the concentration of plasma motilin and serum bile acids in relation to interdigestive gallbladder motility and the MMCs was studied in nine healthy male volunteers. A method combining biliary scintigraphy (99mTc-labelled dimethyl-iminodiacetic acid) and continuous pressure recording from the antroduodenal region was used. During 9 MMC cycles a total of 15 episodes of gallbladder emptying were observed with a median (range) duration of 25 min (15-45 min). Each episode of gallbladder emptying was followed by a steep increase in plasma motilin, reaching a median value of 30 pmol/l (13-43 pmol/l), corresponding to an increase of 18 pmol/l (4-33 pmol/l). The increase in plasma motilin started at the beginning of gallbladder emptying, but the peak value was not reached until a median of 20 min (10-45 min) later. Low plasma motilin concentrations were found between the emptying periods in cases with two or more emptying during the MMC cycle. The serum concentration of bile acids also showed a cyclic variation in relation to gallbladder motility. During periods of gallbladder emptying serum bile acid concentration had a median value of 1.78 mumol/l, as compared with a median value of 1.17 mumol/l during periods of gallbladder filling. This difference did not reach significance, however. In the pooled data from all subjects, a significant correlation (p < 0.01) between the serum concentration of bile acids and plasma concentration of motilin was found. Gallbladder emptying was followed by a steep increase in plasma motilin concentration, and in cases of two or more emptying periods during the MMC cycle the concentration decreased in between. The shape of the serum bile acid profile is dependent on the intestinal transport and absorption of bile acids, and the significance of the cyclic variation in serum concentration of bile acids in relation to plasma motilin, gallbladder motility, and MMC needs further investigation.

Evaluation of the bile acid transporter in enhancing intestinal permeability to renin-inhibitory peptides.

To evaluate the bile acid transporter as a means of enhancing the ability of renin-inhibitory peptides (RIPs) to penetrate the intestinal mucosa, two RIP-cholic acid conjugates and an RIP-taurocholic acid conjugate were synthesized. Conjugation was through the N-terminus of an RIP and the 3-position of the bile acid, via a six-carbon spacer. An RIP derivative containing the spacer without the bile acid moiety was also synthesized. The bile acid-RIP conjugates and the RIP derivative were shown to be potent inhibitors of human renin in vivo and to have in vivo hypotensive activity equivalent to that of the parent RIP (ditekiren) in a human renin-infused rat model. The ability of these RIP derivatives to bind to the bile acid transporter and be transported across an epithelial cell monolayer was evaluated in an in vitro model of the intestinal mucosa consisting of Caco-2 cell monolayers grown on microporous membranes. One of the RIP-cholic acid conjugate (KI = 60 +/- 10 microM) and the RIP-taurocholic acid conjugate (KI = 19 +/- 5 microM), but not the RIP derivative, were shown to be potent inhibitors of the apical (AP) to basolateral (BL) transport of [14C]-taurocholic acid ([14C]-TA). At concentrations up to 250 microM these RIP-bile acid conjugates had no effect on the diffusion of [3H]-PEG (800-1000), which is a marker of the paracellular pathway. The permeability coefficients of the RIP-bile acid conjugates, determined using Caco-2 cell monolayers, were shown to be six times less than that of [3H]-PEG (800-1000). In addition, the transport of one of the RIP-cholic acid conjugates was investigated in perfused rat ileum in which the mesenteric vein was cannulated. The conjugate was not detected in blood samples taken from the mesenteric vein, while its concentration in intestinal perfusate remained almost constant during the perfusion experiment. These results suggest that while the peptide-bile acid conjugates retain binding affinity for the intestinal bile acid transporter, the molecules are not themselves transported.

Hepatic and Intestinal Bile Acid (BA) Transport during Total Parenteral Nutrition (TPN) in the Rat

Hepatic and Intestinal Bile Acid (BA) Transport during Total Parenteral Nutrition (TPN) in the Rat

Bile acid uptake by isolated intestinal mucosa cells of guinea pig

Isolated intestinal mucosa cells of the guinea pig were employed to study intestinal transport of bile acids. Chenodeoxycholate and lithocholate were rapidly taken up into jejunal and ileal cells by diffusion. Taurocholate and cholate however showed only a minor diffusion rate and were preferentially taken up by the ileal bile acid carrier. This uptake was saturable with an apparent K m of 231 μM and V of 7 nmol/mg protein per min for taurocholate; this bile acid was accumulated 90-fold. Its uptake was strongly inhibited by antimycin A, FCCP, ouabain or Na +-deficiency in the medium. Sugars or amino acids did not interfere with uptake. Experimental conditions were optimized with regard to incubation medium, cell amount, cell age and length of preincubation. It is concluded that ileal cells of the guinea pig are superior to other experimental models for characterizing the ileal bile acid carrier, because they allow us to determine initial rates of uptake and have a very efficient energetic coupling.

515 SERUM BILE ACIDS REFLECT THE DEVELOPMENT OF THE ENTEROHEPATIC CIRCULATION IN RATS

We have shown that serum bile acid concentrations are elevated during early life in humans reflecting physiologic immaturity of the enterohepatic circulation. To further define the ontogeny of bile acid metabolism in mammals, we sought maturational changes in the serum values of total cholyl conjugates via a sensitive, specific radioimmunoassay in fetal, suckling, and mature Sprague-Dawley rats.Results: Fetal (21st day) bile acid levels were low (1.42 ± 0.23* μM; x ± SEM) probably due to minimal enterohepatic cycling in utero. With initial suckling, levels rose rapidly (9.27 ± 1.57* on day 1), remained elevated on day 4 (9.63 ± 0.73*), and fell briefly but significantly on day 7 (6.36 ± 0.68, p<0.001 vs day 4). Subsequent elevations were attained stepwise throughout the suckling phase (day 10=7.24 ± 0.57*; day 14=10.47 ± 1.70*, day 21=16.81 ± 1.93*). Following weaning there was a dramatic peak on day 28 (21.76 ± 1.53*); values then fell (5.57 ± 0.68 on day 42) to achieve adult normals by 56 days.Conclusion: Serum bile acid levels reflect sequential developmental maturation of the enterohepatic circulation in the rat. These changes corroborate previous data citing underdeveloped bile canalicular morphology at birth, maturation of intestinal reabsorption, increasing postnatal pool size.before day 56, and persistently impaired hepatic function during normal development. Further studies are warranted to define modulating influences responsible for perinatal physiological and possibly pathophysiological changes in hepatic and intestinal bile acid transport.*p<0.001 vs adult (3.97 ± 0.55 @ 56 day)

Ileal bile salt transport: mutual inhibition in an in vivo system.

ARTICLESIleal bile salt transport: mutual inhibition in an in vivo systemKW Heaton, and L LackKW Heaton, and L LackPublished Online:01 Mar 1968https://doi.org/10.1152/ajplegacy.1968.214.3.585MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByDrug Transport and Membrane Transport Proteins15 September 2010Membrane Transport Proteins and Drug Transport15 January 2003Modeling of active transport systemsAdvanced Drug Delivery Reviews, Vol. 54, No. 3STRUCTURAL BIOLOGY AND FUNCTION OF SOLUTE TRANSPORTERS: IMPLICATIONS FOR IDENTIFYING AND DESIGNING SUBSTRATES27 November 2002 | Drug Metabolism Reviews, Vol. 34, No. 4Effect of Chronic Administration of Tauro-hyodeoxycholic Acid on Biliary Bile Acid Composition and on Biliary Lipid Secretion in Humans8 July 2009 | Scandinavian Journal of Gastroenterology, Vol. 36, No. 9Use of the intestinal and hepatic bile acid transporters for drug deliveryAdvanced Drug Delivery Reviews, Vol. 20, No. 1Intestinal Transport of Bile Acids1 January 2011Active absorption of conjugated bile acids in vivoGastroenterology, Vol. 100, No. 1Effect of chronic administration of ursodeoxycholic acid on the ileal absorption of endogenous bile acids in manHepatology, Vol. 12, No. 5Serum Bile AcidsUtilizing Bile Acid Carrier Mechanisms to Enhance Liver and Small Intestine AbsorptionAnnals of the New York Academy of Sciences, Vol. 507, No. 1 Biological ApIleal absorption of tyrosine-conjugated bile acids in Wistar ratsBiochimica et Biophysica Acta (BBA) - General Subjects, Vol. 926, No. 2Simulation of the metabolism and enterohepatic circulation of endogenous deoxycholic acid in humans using a physiologic pharmacokinetic model for bile acid metabolismGastroenterology, Vol. 93, No. 4Simulation of the metabolism and enterohepatic circulation of endogenous chenodeoxycholic acid in man using a physiological pharmacokinetic modelEuropean Journal of Clinical Investigation, Vol. 16, No. 5Kinetics of Taurocholate Uptake by Isolated Ileal Cells of Guinea PigEuropean Journal of Biochemistry, Vol. 131, No. 2Resorption von GallensäurenBile acid uptake by isolated intestinal mucosa cells of guinea pigBiochimica et Biophysica Acta (BBA) - Molecular Cell Research, Vol. 721, No. 3Properties and biological significance of the ileal bile salt transport system.Environmental Health Perspectives, Vol. 33Pathophysiology of the enterohepatic circulation of bile acids21 June 2005Bile Salt Metabolism:I. The Physiology of Bile Salts25 March 2008 | Australian and New Zealand Journal of Medicine, Vol. 7, No. 6Interaction of uncharged bile salt derivatives with the ileal bile salt transport systemJournal of Lipid Research, Vol. 18, No. 3Dynamics of the Enterohepatic Circulation of the Glycine Conjugates of Cholic, Chenodeoxycholic, Deoxycholic, and Sulfolithocholic Acid in ManGastroenterology, Vol. 72, No. 3Ionic requirements for the active ileal bile salt transport systemJournal of Lipid Research, Vol. 17, No. 6Regional Ileitis (Crohn’s Disease)16 October 2020 | Scandinavian Journal of Gastroenterology, Vol. 11, No. 5Characterization of the passive and active transport mechanisms for bile acid uptake into rat isolated intestinal epithelial cellsBiochimica et Biophysica Acta (BBA) - Biomembranes, Vol. 406, No. 2Interactions of cationic bile salt derivatives with the ileal bile salt transport system.Journal of Lipid Research, Vol. 16, No. 5Effects of meals and interruption of enterohepatic circulation on flow, lipid composition, and cholesterol saturation of bile in man after cholecystectomyThe American Journal of Digestive Diseases, Vol. 20, No. 2Effect of Phenobarbital on Intestinal Cholic Acid Absorption in the RatGastroenterology, Vol. 67, No. 6Bile Salt Transport SystemsIleal transport of bile acids conjugated with norleucine and lysineBiochimica et Biophysica Acta (BBA) - Biomembranes, Vol. 266, No. 1Transport of DrugsThe Enterohepatic CirculationGastroenterology, Vol. 62, No. 1Metabolism and transport of bile salts in the intestineThe American Journal of Medicine, Vol. 51, No. 5Changes in Fat Absorption following small Bowel Resection in the Dog27 September 2008 | Archives Internationales de Physiologie et de Biochimie, Vol. 79, No. 5Morphological changes of the small-intestinal mucosa of guinea pig and hamster following incubation in vitro and perfusion in vivo with unconjugated bile saltsGut, Vol. 11, No. 6Effects of Sulfation of Taurolithocholic and Glycolithocholic Acids on their Intestinal TransportGastroenterology, Vol. 56, No. 4 More from this issue > Volume 214Issue 3March 1968Pages 585-590 Copyright & PermissionsCopyright © 1968 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1968.214.3.585PubMed5644097History Published online 1 March 1968 Published in print 1 March 1968 Metrics