ISSN:
1432-1424
Keywords:
nucleoside transport
;
uridine
;
nitrobenzylthioinosine (NBMPR)
;
plasma membrane vesicles
;
rat liver
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary The characteristics of uridine transport were studied in basolateral plasma membrane vesicles isolated from rat liver. Uridine was not metabolized under transport measurement conditions and was taken up into an osmotically active space with no significant binding of uridine to the membrane vesicles. Uridine uptake was sodium dependent, showing no significant stimulation by other monovalent cations. Kinetic analysis of the sodium-dependent component showed a single system with Michaelis-Menten kinetics. Parameter values were K M 8.9 μ m and V max 0.57 pmol/mg prot/sec. Uridine transport proved to be electrogenic, since, firstly, the Hill plot of the kinetic data suggested a 1 uridine: 1 Na+ stoichiometry, secondly, valinomycin enhanced basal uridine uptake rates and, thirdly, the permeant nature of the Na+ counterions determined uridine transport rates (SCN− 〉 NO 3 − 〉 Cl− 〉 SO 4 2− ). Other purines and pyrimidines cis-inhibited and trans-stimulated uridine uptake.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00231815
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