Rana catesbeiana Oocytes: An Alternative To The Xenopus laevis Heterologous Expression System For Ammonia Transporters

Xenopus laevis oocytes are a valuable tool for understanding the transport of H2O, CO2 and/or ammonia (NH3/NH4+) through mammalian aquaporins (AQPs), the glycosylated Rhesus (Rh) proteins (AG, BG and CG) and the urea transporter UT-B, membrane proteins expressed in tissues involved in ammonium homeostasis and/or transport, such as the liver and the kidney. This is the actual focus of our research; however, regulations in Brazil render the import of Xenopus laevis frogs impractical. Here we evaluate the usefulness of North American aquatic bullfrog Rana catesbeiana, which is freely commercialized in Brazil, as an alternative. We have developed a collagenase-based method for isolating individual defolliculated oocytes from Rana ovaries. We find that they are a similar size to Xenopus oocytes and are amenable to injection with cRNA, surface biotinylation protocols, western blot analysis, and measurements of osmotic water permeability (Pf) using a video camera to monitor the projection area of the oocyte as w...