Presence of ranatensin-like and bombesin-like peptides in amphibian brains.

Antibodies specific for the carboxyl-terminal regions of bombesin and of ranatensin were used to study the tissue distribution of substances immunochemically similar to these two peptides in three amphibian species. Brain extracts of Rana catesbeiana, Rana pipiens, and Xenopus laevis all contained considerable quantities of both types of immunoreactivity, with measured concentrations as high as several hundred pmol per g tissue. The two antibodies used in this study had very low crossreactivity (less than 1% by RIA) with the other peptide. In addition, gel filtration revealed different elution profiles for the two immunoreactive substances extracted from amphibian brains. Immunocytochemistry revealed differences in localization within nerve fibers and cell bodies and specific absorption by the appropriate peptide. Ranatensin-like peptides were also present in high concentrations in skin of the two Rana species but not in that of Xenopus. Bombesin-like peptides were more abundant in the stomach of all three species. Significant amounts of substance P/phylasaemin-like immunoreactivity also were detected in the brains of all three species. It is concluded that ranatensin-like peptides are not confined to the skin and can be included as central nervous system neuropeptides in amphibians. These two groups of peptides are not species-specific since both are found in brain and stomach of amphibians whose skin contains only ranatensin-like peptide or neither.