Cellular localization of sulfobromophthalein transport activity in rat liver

Baldini, Giulia; Passamonti, Sabina; Lunazzi, Gian Carlo; Tiribelli, Claudio; Sottocasa, Gian Luigi

doi:10.1016/0005-2736(86)90002-7

Cited by 48 publications

(49 citation statements)

References 19 publications

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“…The hepatic uptake of BSP and DBSP is electrogenic (Baldini et al 1986;Potter et al 1987b;Persico and Sottocasa 1987;) and involves the quinoid, deprotonated moiety of the ligand ( Fig. 9; Persico and Sottocasa 1987;Passamonti and Sottocasa 1988;Torres et al 1990).…”

Section: Bromosulfophthalein and Derivativesmentioning

confidence: 99%

“…The protein has been reconstituted into artificial liposomes and in erythrocyte membranes ), both of which transported BSP. Erythrocytes do not transport BSP normally (Baldini et al 1986). Bilitranslocase has also been immunologically localized in basolateral plasma membrane vesicles prepared from rat kidney cortex (Elias et al 1990).…”

Section: Carrier Proteins For Hepatic Uptake Of Cholephilic Organic Amentioning

confidence: 99%

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Transport of organic anions in the liver. An update on bile acid, fatty acid, monocarboxylate, anionic amino acid, cholephilic organic anion, and anionic drug transport

Petzinger¹

1994

Reviews of Physiology, Biochemistry and Pharmacology

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Section: Bromosulfophthalein and Derivativesmentioning

confidence: 99%

Section: Carrier Proteins For Hepatic Uptake Of Cholephilic Organic Amentioning

confidence: 99%

Transport of organic anions in the liver. An update on bile acid, fatty acid, monocarboxylate, anionic amino acid, cholephilic organic anion, and anionic drug transport

Petzinger¹

1994

Reviews of Physiology, Biochemistry and Pharmacology

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“…Bilitranslocase is a plasma membrane carrier (Sottocasa et al 1989) expressed at the basolateral (sinusoidal) domain of the hepatocytes (Baldini et al 1986). Its physiological role is to mediate the membrane transport of organic anions from blood to liver (Sottocasa et al 1996;Passamonti & Sottocosa 2002).…”

Section: Introductionmentioning

confidence: 99%

Immunolocalisation of bilitranslocase in mucosecretory and parietal cells of the rat gastric mucosa

et al. 2005

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Bilitranslocase is a plasma membrane carrier localised at the vascular pole of the rat liver cell, where it mediates uptake of organic anions from the blood into the liver. This carrier is also present in the epithelium of the rat gastric mucosa, with similar molecular mass and functional properties. An immunohistochemical study reveals that both the mucus-secreting cells of the gastric pit and the H+-secreting parietal cells express bilitranslocase. These data point to a possible role of bilitranslocase and of its food-borne substrates (anthocyanins and nicotinic acid) in regulating the function and the permeability of the gastric mucosa.

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“…However, the cellular uptake of bilirubin and BSP can be dissociated (14, 15), suggesting distinct transport mechanisms. While it has been argued that the unique "permeability" of hepatocytes to bilirubin confirms the presence of a specific transporter (12,16), other studies have demonstrated nonsaturable and non-energy-dependent bilirubin uptake (17), indicative of a diffusional process. Moreover, fibroblasts transfected with cDNA for the bilirubin-conjugating enzyme, UDPglucuronosyltransferase, do not express any of the candidate transporters yet are effectively able to take up and conjugate bilirubin (18).…”

mentioning

confidence: 99%

Unconjugated Bilirubin Exhibits Spontaneous Diffusion through Model Lipid Bilayers and Native Hepatocyte Membranes

Zucker

Goessling

Hoppin

1999

Journal of Biological Chemistry

122

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The liver is responsible for the clearance and metabolism of unconjugated bilirubin, the hydrophobic endproduct of heme catabolism. Although several putative bilirubin transporters have been described, it has been alternatively proposed that bilirubin enters the hepatocyte by passive diffusion through the plasma membrane. In order to elucidate the mechanism of bilirubin uptake, we measured the rate of bilirubin transmembrane diffusion (flip-flop) using stopped-flow fluorescence techniques. Unconjugated bilirubin rapidly diffuses through model phosphatidylcholine vesicles, with a first-order rate constant of 5.3 s ؊1 (t1 ⁄2 ‫؍‬ 130 ms). The flip-flop rate is independent of membrane cholesterol content, phospholipid acyl saturation, and lipid packing, consistent with thermodynamic analyses demonstrating minimal steric constraint to bilirubin transmembrane diffusion. The coincident decrease in pH of the entrapped vesicle volume supports a mechanism whereby the bilirubin molecule crosses the lipid bilayer as the uncharged diacid. Transport of bilirubin by native rat hepatocyte membranes exhibits kinetics comparable with that in model vesicles, suggesting that unconjugated bilirubin crosses cellular membranes by passive diffusion through the hydrophobic lipid core. In contrast, there is no demonstrable flip-flop of bilirubin diglucuronide or bilirubin ditaurate in phospholipid vesicles, yet these compounds rapidly traverse isolated rat hepatocyte membranes, confirming the presence of a facilitated uptake system(s) for hydrophilic bilirubin conjugates.Unconjugated bilirubin is the principal degradation product of heme metabolism. Although the physiologic isomer, bilirubin IX␣, is a dicarboxylic acid, the molecule has minimal aqueous solubility at physiologic pH (1, 2) due to the formation of intramolecular hydrogen bonds (3). For this reason, bilirubin undergoes biotransformation in the liver to more polar conjugates prior to secretion in the bile. However, while unconjugated bilirubin is not hydrophilic, neither can it be characterized as lipophilic (1), since this compound is equally insoluble in apolar solvents (e.g. n-hexane, 1-pentanol). These unique physical-chemical properties have generated controversy regarding the mechanism of bilirubin uptake by the liver. Based on the spontaneous leakage from multilamellar liposomes (4), it has been proposed that bilirubin is able to diffuse through cellular membranes (5, 6). On the other hand, in vivo (7) and whole organ (8, 9) studies indicate that hepatic bilirubin uptake is saturable and occurs against a concentration gradient, findings that support a protein-mediated transport mechanism. To date, four putative bilirubin transporters have been identified in liver cells: BSP/bilirubin-binding protein, organic anion-transporting polypeptide, bilitranslocase, and organic anion-binding protein. Each of these proteins facilitates uptake of the hydrophilic organic anion, sulfobromophthalein (BSP), 1 a process that is competitively inhibited by bilirubin (10, 11).However, des...

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Cellular localization of sulfobromophthalein transport activity in rat liver

Cited by 48 publications

References 19 publications

Transport of organic anions in the liver. An update on bile acid, fatty acid, monocarboxylate, anionic amino acid, cholephilic organic anion, and anionic drug transport

Transport of organic anions in the liver. An update on bile acid, fatty acid, monocarboxylate, anionic amino acid, cholephilic organic anion, and anionic drug transport

Immunolocalisation of bilitranslocase in mucosecretory and parietal cells of the rat gastric mucosa

Unconjugated Bilirubin Exhibits Spontaneous Diffusion through Model Lipid Bilayers and Native Hepatocyte Membranes

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