Size Selected mRNA Induces Expression of P-Aminohippurate Transport in Xenopus Oocytes

Xenopus oocytes were injected with size-fractionated mRNA isolated from the renal cortex of rabbit kidney and after 4 days incubation, PAH uptake in oocytes injected with mRNA (0.7 - 1.3 kb) was 8 to 45 fold that of the water injected controls. The oocyte to medium ratio of accumulated PAH was 1.95. The Km and Vmax for transport were 333 μM and 66.6 nmoles·oocyte⁻¹· min^−l, respectively. This Km is similar to that reported for PAH transport in intact kidneys and slices. The uptake of PAH was unaffected by the absence of Na⁺ or the presence of probenecid. Expression of the transport represents the first step in an effort to clone and identify the gene for PAH transport.