Document Detail


Interaction of porphyrins with human organic anion transporting polypeptide 1B1.
MedLine Citation:
PMID:  19560444     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The existence of a porphyrin uptake transporter in hepatocytes has been hypothesized in recent years, but to date it has not been identified. While the linear tetrapyrrole bilirubin has been shown to be a substrate for the organic anion transporting polypeptide 1B1 (OATP1B1), similar studies have not been conducted for the cyclic tetrapyrroles (porphyrins). The aim of this study was to determine the structural features of linear and cyclic tetrapyroles necessary for interaction with OATP1B1. The interaction was quantified using HEK cells stably expressing OATP1B1 and measuring the inhibition of OATP1B1-mediated uptake of estradiol 17beta-d-glucuronide in the presence or absence of various linear and cyclic tetrapyrroles. Ditaurine-conjugated bilirubin was the most potent inhibitor of uptake, with an IC50 of 5 nM, while the substitution of the taurine side chains with methyl ester eliminated the inhibition of estradiol 17beta-d-glucuronide uptake. Hematoporphyrin, a cyclic tetrapyrrole with carboxyalcohol side chains at positions C-3 and C-8 and carboxyethyl side chains at positions 13 and 17 had an IC50 of 60 nM, while porphyrins lacking charged side chains such as etioporphyrin I and phthalocyanine did not inhibit OATP1B1. Chlorin e6 and hematoporphyrin were shown to be competitive inhibitors of OATP1B1-mediated uptake of bromosulfophthalein with Kis of 5.8+/-0.3 and 1.6+/-0.3 microM, respectively. While these studies do not provide direct evidence, they do support the assumption that tetrapyrroles are transported by OATP1B1. Additionally, these findings offer a possible explanation for the clinical observation that patients suffering from certain porphyrietic diseases have a reduced ability to excrete organic anions.
Authors:
Scott D Campbell; Wan F Lau; Jinghai J Xu
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Publication Detail:
Type:  Journal Article     Date:  2009-06-26
Journal Detail:
Title:  Chemico-biological interactions     Volume:  182     ISSN:  1872-7786     ISO Abbreviation:  Chem. Biol. Interact.     Publication Date:  2009 Nov 
Date Detail:
Created Date:  2009-10-05     Completed Date:  2009-10-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0227276     Medline TA:  Chem Biol Interact     Country:  Ireland    
Other Details:
Languages:  eng     Pagination:  45-51     Citation Subset:  IM    
Affiliation:
Division of Clinical and Translational Research, Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA. campbels@wustl.edu
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MeSH Terms
Descriptor/Qualifier:
Binding Sites
Binding, Competitive
Biological Transport
Cell Line
Estradiol / analogs & derivatives*,  metabolism,  pharmacokinetics
Humans
Inhibitory Concentration 50
Models, Molecular
Organic Anion Transporters / antagonists & inhibitors,  biosynthesis,  genetics,  metabolism*
Porphyrins / metabolism,  pharmacokinetics*
Sulfobromophthalein / metabolism
Transfection
Chemical
Reg. No./Substance:
0/Organic Anion Transporters; 0/Porphyrins; 0/SLCO1B1 protein, human; 1806-98-0/estradiol-17 beta-glucuronide; 297-83-6/Sulfobromophthalein; 50-28-2/Estradiol

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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