Shayeghi, M. and Akerman, R. and Jarvis, S.M. (1999) Nucleobase transport in opossum kidney epithelial cells and Xenopus laevis oocytes: the characterisation, structure-activity relationship of uracil analogues and oocyte expression studies of sodium-dependent and -independent hypoxanthine uptake. Biochimica Et Biophysica Acta-Biomembranes, 1416 (1-2). pp. 109-118. ISSN 0005-2736.
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The characteristics of hypoxanthine transport were examined in opossum kidney (OK) epithelial cells and Xenopus laevis oocytes. In both cell types hypoxanthine influx was mediated by two distinct transport systems: a high-affinity Na+-dependent system and a Na+-independent transporter. Na+-dependent hypoxanthine transport in OK cells was saturable (K-m 0.78 +/- 0.29 mu M) and was inhibited by guanine, uracil, thymine and 5-fluorouracil (K-i values 0.5-7 mu M), whereas adenine had no effect. Substitutions at the 2- and 4-position had a marked effect on the ability of uracil to inhibit Na+/hypoxanthine influx by OK cells revealing that an oxo group at both the 2- and 4-positions of uracil is required for interacting with the transporter. The properties of Na+-dependent hypoxanthine influx in oocytes were similar to those observed in OK cells. In particular, xanthine and oxypurinol inhibited hypoxanthine influx, a characteristic not observed previously for the Na+/nucleobase carrier in pig LLC-PK1 renal cells. Na+-independent hypoxanthine influx in OK cells and oocytes was of a lower affinity (K-m 90-180 mu M). Adenine and guanine inhibited Na+-independent hypoxanthine flux in OK cells, but had no effect in oocytes. Injection of LLC-PK1 mRNA into oocytes resulted in a 1.5-fold stimulation of Na+/hypoxanthine flux over water-injected oocytes. These results reveal further heterogeneity in Na+/nucleobase cotransporters.
|Uncontrolled keywords:||nucleobase transport; kidney; uracil analog; expression cloning; hypoxanthine|
Q Science > QD Chemistry
Q Science > QH Natural history > QH301 Biology
Q Science > QC Physics
|Divisions:||Faculties > Science Technology and Medical Studies > School of Biosciences|
|Depositing User:||F.D. Zabet|
|Date Deposited:||26 Mar 2009 12:03|
|Last Modified:||26 Mar 2009 12:03|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/16615 (The current URI for this page, for reference purposes)|
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