Ligand-binding studies revealed the presence of GnRH-binding sites in African catfish ovary. However, our expression profiling studies failed to detect the previously identified catfish GnRH receptor (cfGnRH-R1) mRNA in this tissue. This negative result instigated us to clone an additional catfish GnRH receptor (cfGnRH-R2) cDNA and study its expression in different tissues in conjunction with the expression of the two catfish GnRH (i.e. cfGnRH and cGnRH-II) genes. The highest cfGnRH-R1 and cfGnRH-R2 mRNA levels were detected in pituitary for cfGnRH-R1 and in brain and ovary for cfGnRH-R2. cfGnRH mRNA was coexpressed with cfGnRH-R1 mRNA in pituitary and brain and with cfGnRH-R2 mRNA in brain and ovary. Ubiquitous expression of cGnRH-II mRNA was observed in all tissues tested, with the highest expression in brain, heart, pituitary, ovary, and head-kidney. Binding studies revealed that cfGnRH-R1 had a higher affinity than cfGnRH-R2 for cGnRH-II, cfGnRH, and various other GnRH agonists. However, this was not reflected in the inositol phosphate or cAMP signal transduction properties of both types of cfGnRH-R. We therefore conclude that in catfish, functional ligand/receptor units evolved by restricted coexpression of a particular receptor in combination with a particular GnRH in particular (nearby) tissue(s).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.