ABSTRACT
Oocytes of the frog Xenopus laevis are a well-studied system that has been widely used in biomedical research. Much of what we know about the basic biology of the oocyte has helped to develop it as a system for exogenous ion channels and membrane receptor expression. Because Xenopus oocytes offer many experimental advantages, they are commonly used in laboratories interested in understanding the characteristics of membrane proteins involved in neuronal transmission and cell-to-cell communication.
Ricardo Miledi showed that functional ion channels and receptors could be expressed by injecting mRNA and using electrophysiological techniques to assess their activity. A second approach advanced the field when cDNA clones encoding for specific proteins were tested in the oocyte by injecting DNA into the nucleus or synthetic RNA into the cytoplasm. More recently, a novel assay allows scientists to measure the activity of ion channels and receptors transplanted from plasma membranes isolated from brain tissue.
Oocytes and ovarian follicles also express a plethora of “native” endogenous ion channels, G protein-coupled receptors, and receptor channels that are worth studying in their own right. Such are the cases of oxytocin, progesterone, and angiotensin responses, as well as the electric responses generated by chloride and potassium channels.
