title: Basolateral uptake of nucleosides by Sertoli cells is mediated primarily by equilibrative nucleoside transporter 1.
abstract: The blood-testis barrier (BTB) prevents the entry of many xenobiotic compounds into seminiferous tubules thereby protecting developing germ cells. Understanding drug transport across the BTB may improve drug delivery into the testis. Members of one class of drug, nucleoside reverse transcriptase inhibitors (NRTIs), do penetrate the BTB, presumably through interaction with physiologic nucleoside transporters. By investigating the mechanism of nucleoside transport, it may be possible to design other drugs to bypass the BTB in a similar manner. We present a novel ex vivo technique to study transport at the BTB that employs isolated, intact seminiferous tubules. Using this system, we found that over 80% of total uptake by seminiferous tubules of the model nucleoside uridine could be inhibited by 100 nM nitrobenzylmercaptopurine riboside (NBMPR, 6-S-[(4-nitrophenyl)methyl]-6-thioinosine), a concentration that selectively inhibits equilibrative nucleoside transporter 1 (ENT1) activity. In primary cultured rat Sertoli cells, 100 nM NBMPR inhibited all transepithelial transport and basolateral uptake of uridine. Immunohistochemical staining showed ENT1 to be located on the basolateral membrane of human and rat Sertoli cells, whereas ENT2 was located on the apical membrane of Sertoli cells. Transepithelial transport of uridine by rat Sertoli cells was partially inhibited by the NRTIs zidovudine, didanosine, and tenofovir disoproxil fumarate, consistent with an interaction between these drugs and ENT transporters. These data indicate that ENT1 is the primary route for basolateral nucleoside uptake into Sertoli cells and a possible mechanism for nucleosides and nucleoside-based drugs to undergo transepithelial transport.
authors: Department of Pharmacology and Toxicology, University of Arizona, Tucson, Arizona, USA.
authors: David M
authors: DM
authors: Klein
authors: Kristen K
authors: KK
authors: Evans
authors: Rhiannon N
authors: RN
authors: Hardwick
authors: William H
authors: WH
authors: Dantzler
authors: Stephen H
authors: SH
authors: Wright
authors: Nathan J
authors: NJ
authors: Cherrington
mesh_terms: D000328:Adult; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001814:Blood-Testis Barrier / Q000187:drug effects / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity; D002478:Cells, Cultured; D033721:Equilibrative Nucleoside Transporter 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D033722:Equilibrative-Nucleoside Transporter 2 / Q000378:metabolism*; D006801:Humans; D008297:Male; D049990:Membrane Transport Modulators / Q000494:pharmacology; D051379:Mice; D009705:Nucleosides / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D018894:Reverse Transcriptase Inhibitors / Q000378:metabolism*; D012671:Seminiferous Tubules / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D012708:Sertoli Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D014529:Uridine / Q000378:metabolism
chemical_list: D033721:Equilibrative Nucleoside Transporter 1; D033722:Equilibrative-Nucleoside Transporter 2; D049990:Membrane Transport Modulators; D009705:Nucleosides; D018894:Reverse Transcriptase Inhibitors; C438649:SLC29A1 protein, human; C438654:SLC29A2 protein, human; D014529:Uridine
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