EXPRESSION OF THE RABBIT INTESTINAL N2 NA+ NUCLEOSIDE TRANSPORTER IN XENOPUS-LAEVIS OOCYTES

Polyadenylated [poly(A)+] mRNA isolated from rabbit small-intestinal mucosa was injected into Xenopus laevis oocytes, and expression of the N2 Na+/nucleoside co-transporter was assayed by measuring Na+-dependent thymidine uptake. Expression of Na+-dependent thymidine uptake steadily increased after mRNA injection and was on average increased 11-fold by day 6 over background. Na+-dependent thymidine uptake was saturable (apparent K(m) approximately 30-mu-M at 22-degrees-C) and inhibited by uridine and cytidine, but not by guanosine and inosine. These properties of the expressed thymidine transport strongly suggest that the epithelial N2 Na+/nucleoside co-transporter can be expressed in X. laevis oocytes.