Endothelin receptor: a profoundly desensitizing receptor expressed in Xenopus oocytes

Xenopus oocyte expression studies can help to define the physiological properties of a receptor and can aid in receptor cloning. Expression of an endothelin receptor in oocytes injected with brain mRNA is inferred from depolarizations induced by several endothelin-related peptides. The response is abolished by intracellular EGTA injection but not in the absence of extracellular Ca²⁺. It is not present in non-injected oocytes, and reverses at a potential indicating that it is mediated by an increased Cl^-1 conductance. Responses display striking, long-lasting desensitization. The expressed endothelin receptor thus displays properties characteristic of several receptors coupled to changes in phosphoinositide turnover, several of which have been successfully cloned using this response as a reporter.