Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0262471 (ENT)
 5,307 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The olfactory neuro-epithelium is highly sensitive to chemicals and its direct microbiological environment. It also plays a role as an interface between the airways and the nervous system, and so it has developed several defence instruments for rapid regeneration or for the detoxification of the immediate environment. This review illustrates three of these defence mechanisms: regeneration of the epithelium, local production of metabolising enzymes and xenobiotic transporters. Toxicants can inflict damage by a direct toxic response. Alternatively, they may require metabolic activation to produce the proximate toxicant. In addition to detoxifying inhaled and systemically derived xenobiotics, the local olfactory metabolism may fulfil multiple functions such as the modification of inhaled odorant, the modulation of endogenous signalling molecules and the protection of other tissues such as the CNS and lungs from inhaled toxicants. Finally, the permeability of nasal and olfactory mucosa is an important efficacy parameter for some anti-allergic drugs delivered by intranasal administration or inhalation. Efflux or update transporters expressed in these tissues may therefore significantly influence the pharmacokinetics of drugs administered topically.
B-ENT 2009
PMID:Defence mechanisms of olfactory neuro-epithelium: mucosa regeneration, metabolising enzymes and transporters. 2008 3

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.
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PMID:Basolateral uptake of nucleosides by Sertoli cells is mediated primarily by equilibrative nucleoside transporter 1. 2363