Distribution of equilibrative, nitrobenzylthioinosine-sensitive nucleosidetransporters (ENT1) in brain

Nucleoside transport processes may play a role in regulating endogenous lev els of the inhibitory neuromodulator adenosine in brain. The cDNAs encoding species homologues of one member of the equilibrative nucleoside transport er (ENT) gene family have recently been isolated from rat (rENT1) and human (hENT1) tissues. The current study used RT-PCR, northern blot, in situ hyb ridization, and [H-3]nitrobenzylthioinosine autoradiography to determine th e distribution of mRNA and protein for ENT1 in rat and human brain. Norther n blot analysis indicated that hENTI mRNA is widely distributed in adult hu man brain. S-35-labeled sense and antisense riboprobes, transcribed from a 153-bp segment of rENT1, were hybridized to fresh frozen coronal sections f rom adult rat brain and revealed widespread rENT1 mRNA in pyramidal neurons of the hippocampus, granule neurons of the dentate gyrus, Purkinje and gra nule neurons of the cerebellum, and cortical and striatal neurons. Regional localization in rat brain was confirmed by RT-PCR, Thus, ENT1 mRNA has a w ide cellular and regional distribution in brain, indicating that this nucle oside transporter subtype may be important in regulating intra- and extrace llular levels of adenosine in brain.