GONADOTROPIN-RELEASING-HORMONE IN ELASMOBRANCH (ELECTRIC RAY, TORPEDO-MARMORATA) BRAIN AND PLASMA - CHROMATOGRAPHIC AND IMMUNOLOGICAL EVIDENCE FOR CHICKEN GNRH-II AND NOVEL MOLECULAR-FORMS

Gonadotropin-releasing hormone (GnRH) peptides in the brain, testis an d plasma of an electric ray (Torpedo marmorata) were investigated by g el filtration chromatography, reverse phase high performance liquid ch romatography and radioimmunoassay with region-specific antisera. In th e brain, two major forms of GnRH were demonstrated. One form had ident ical chromatographic and immunological properties to chicken GnRH II, and the second, novel. molecular form had structural features in commo n with mammalian, chicken II and salmon GnRHs. A minor, early-eluting immunoreactive peak, possibly also a novel GnRH. was also evident. Imm unoreactive GnRH was not detected in the testis. In the plasma, a sing le major early-eluting immunoreactive peak was demonstrated. This peak , identical to the minor peak observed in the brain, is likely to repr esent a novel form of GnRH which has immunological properties in commo n with mammalian, chicken II and salmon GnRHs. Immunoreactive GnRH was not detected in the plasma of species from other vertebrate classes, including rabbit, chicken, monitor lizard, clawed toad, frog, cichlid fish and lamprey. The finding of chicken GnRH II in a species of Chond richthyes adds further support to our hypothesis that this widespread structural variant may represent an early-evolved and conserved form o f GnRH. The presence of a GnRH molecular form in the plasma of the ele ctric ray suggests that GnRH may reach target organs (pituitary and go nads) via the general circulation in some species of Chondrichthyes.