Differential binding of mammalian and salmon GnRHs with rat and carp pituitary receptors.

OBJECTIVES: Receptor binding of GnRH is connected with the stimulation of pituitary gonadotropic cells leading to both the release and biosynthesis of gonadotropins. The binding is connected with the conformational changes in the receptor which induce the specific intracellular signalisation. The study of fish GnRHs and their receptors may give us new knowledge of the complex interplay of different mechanisms involved in neuroendocrine regulation of reproduction.

METHODS: Receptor binding of both mGnRH and sGnRH were compared by the study utilizing the displacement method with mGnRH or sGnRH as radioactive tracers. Incubation was performed at 2 degrees C to avoid ligand degradation.

RESULTS: The comparative binding of mGnRH and sGnRH with GnRH receptors from the female rat pituitary and female carp pituitary was studied. At the 50% of displacement, the binding of sGnRH to the rat pituitary receptor was very small and in comparison to the binding of mGnRH (100%) was in the range 2-15%. However, the binding of mGnRH to carp pituitary receptors is small in comparison with the binding of sGnRH (100%) and was in the range 5-20%.

CONCLUSION: The results demonstrated the differences in binding of different GnRHs to the receptor in rats and carp. This suggests that the structures of GnRH and its receptor undergo co-evolution in different classes of animals.