Expression of a renal Na-nucleoside cotransport system (N2) in Xenopus laevis oocytes.

Xenopus laevis oocytes have been used for the expression of a renal, pyrimidine-selective, Na-nucleoside cotransporter (N2). As compared to its uptake in water-injected oocytes, Na-dependent thymidine uptake was enhanced in a time- and dose- dependent manner in oocytes injected with rat renal cortex total poly(A) RNA. An increased uptake was also observed after injection of size fractionated rat renal cortex poly(A) RNA (2-3 kb). Consistent with the selectivity of the N2 nucleoside transporter, cytidine significantly inhibited Na-dependent thymidine uptake in oocytes injected with total poly(A) RNA whereas guanosine and formycin B did not. Na-dependent thymidine uptake was also enhanced in oocytes injected with size fractionated human renal cortex poly(A) RNA (2-3 kb). The above data demonstrate functional expression of renal cortex, Na-nucleoside cotransporters in Xenopus laevis oocytes. [ABSTRACT FROM AUTHOR]