4.5 Article

Quantification of ENT1 and ENT2 Proteins at the Placental Barrier and Contribution of These Transporters to Ribavirin Uptake

Journal

JOURNAL OF PHARMACEUTICAL SCIENCES
Volume 108, Issue 12, Pages 3917-3922

Publisher

ELSEVIER SCIENCE INC
DOI: 10.1016/j.xphs.2019.09.005

Keywords

drug transport; membrane transporter(s); nucleoside transporter; pharmacokinetics; placenta; pregnancy

Funding

  1. JSPS KAKENHI [16J05272, 15K15007, 26282028]
  2. MEXT-Supported Program for Strategic Research at Private Universities
  3. Food Safety Commission of Japan (Cabinet Office) [1107]
  4. Keio Gijuku Academic Development Fund
  5. Uehara Memorial Foundation
  6. Mochida Memorial Foundation for Medical and Pharmaceutical Research
  7. Hoansha Foundation
  8. Grants-in-Aid for Scientific Research [26282028, 15K15007, 16J05272] Funding Source: KAKEN

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The aims of this study are to quantify the protein levels of nucleoside transporters in placental microvillous membranes (MVMs) and to clarify the contributions of these transporters to ribavirin uptake at the placental barrier. Placental MVMs of human and rat expressed equilibrative nucleoside transporter (ENT) 1 protein, whereas the expression of ENT2 protein was obscure. Maternal-to-fetal transfer of [H-3] ribavirin in rats was much higher than that of [C-14]sucrose. The uptake of [H-3]ribavirin by rat placental trophoblast TR-TBT 18 d-1 cells, which functionally express both ENT1 and ENT2 proteins, was saturable, and was significantly inhibited by 0.1 mu M nitrobenzylthioinosine, which selectively abolishes ENT1-mediated uptake. Dipyridamole at 10 mu M is capable of inhibiting ENT2 as well as ENT1, but a degree of inhibition by 10 mu M dipyridamole on [H-3]ribavirin uptake was not much different from that by 0.1 mM nitrobenzylthioinosine (ENT1-specific inhibitor). Therefore, ENT2 may contribute little to [H-3] ribavirin uptake by these cells. Rat ENT1 cRNA-injected oocytes showed increased [H-3]ribavirin uptake compared with water-injected oocytes, while rat ENT2 cRNA-injected oocytes did not. In conclusion, ENT1 protein expressed in placental MVMs appears to play a predominant role in the uptake of ribavirin. (C) 2019 The Authors. Published by Elsevier Inc. on behalf of the American Pharmacists Association (R).

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