Brain-to-blood efflux transport of estrone-3-sulfate at the blood-brain barrier in rats

Ken Ichi Hosoya, Hiroshi Asaba, Tetsuya Terasaki

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31 Citations (Scopus)

Abstract

Efflux transport of estrogens such as estrone-3-sulfate (E1S), and estrone (E1) across the blood-brain barrier (BBB) was evaluated using the Brain Efflux Index (BEI) method. The apparent BBB efflux rate constant (K(eff)) of [3H]E1S, and [3H]E1 was 6.63 X 10-2 ± 0.77 X 10 -2 min -1, and 6.91 X 10-2 ± 1.23 X 10-2 min-1, respectively. The efflux transport of [3H]E1S from brain across the BBB was a saturable process with Michaelis constant (K(m))of 96.0 ± 34.4 μM and 93.4 ± 22.0 μM estimated by two different methods. By determining [3H]E1S metabolites using high performance liquid chromatography (HPLC) after intracerebral injection, significant amounts of [3H]E1S were found in the jugular venous plasma, providing direct evidence that most of [3H]E1S is transported from brain across the BBB in intact form. To compare the apparent efflux clearance across the BBB of E1S with that of E1, the brain distribution volume of E1S and E1 was estimated using the brain slice uptake method. The apparent efflux clearance of [3H]E1S was determined to be 74.9 ± 3.8 μl/(min·g brain) due to the distribution volume of 1.13 ± 0.06 ml/g brain. By contrast, the apparent efflux clearance of E1 was more than 227 ± 3 μl/(min·g brain), since the distribution volume of [3H]E1 at 60 min was 3.28 ± 0.13 ml/g. The E1S efflux transport process was inhibited by more than 40% by coadministration of bile acids (taurocholate, and cholate), and organic anions (sulfobromophthalein, and probenecid), whereas other organic anions did not affect the E1S efflux transport. The [3H]E1S efflux was significantly reduced by 48.6% after preadministration of 5 mM dehydroepiandrosterone sulfate. These results suggest that E1S is transported from brain to the circulating blood across the BBB via a carrier-mediated efflux transport system. (C) 2000 Elsevier Science Inc.

Original languageEnglish
Pages (from-to)2699-2711
Number of pages13
JournalLife Sciences
Volume67
Issue number22
DOIs
Publication statusPublished - 2000 Oct 20

Keywords

  • Blood-brain barrier
  • Efflux transport
  • Estrone-3-sulfate
  • Organic anion transporting polypeptide

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)

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