Gonadotropin-releasing hormone in ratfish (Hydrolagus colliei): distribution between the sexes and possible relationship with chicken II and salmon II forms.

1. Brain extract from the spotted ratfish, Hydrolagus colliei, contains gonadotropin-releasing hormone (GnRH)-like peptides in both sexes. 2. The dominant form occurs with a concentration of 0.5-1.7 ng/g frozen brain tissue in males, and 1.3-2.5 ng/g in females. 3. A similar pattern of GnRH immunoreactivity and chromatographic behaviour are found in both sexes. 4. A semipurified extract of this peptide could not be distinguished chromatographically from either chicken II or salmon II forms of the peptide. 5. The ratfish represents the most primitive organism that contains a form of GnRH that coelutes with chicken II and salmon II GnRH.