Immunoreactive calcitonin in the central nervous system of the pigeon

To determine whether calcitonin (CT) is present in avian central nervous system (CNS), as it has been recently found in the CNS of other species, we studied extracts of pigeon (Columbia livia) brain by immunochemical methods. A sensitive and specific radioimmunoassay for salmon CT was used together with gel filtration and high performance liquid chromatography (HPLC). Extracts of hypothalamus contained 31.5 +/- 9.65 ng/g wet weight as salmon CT-like immunoreactivity while extracts of midbrain and brain stem contained 17.0 +/- 5.00 and 2.85 +/- 2.1 ng/g wet weight respectively. Extracts of whole pituitary gland, other areas of the CNS and vazrious peripheral tissues were below the detection limits of our assay, but salmon CT-like immunoreactivity was present in ultimobranchial gland (UBG), thyroid gland and lung tissue extracts. On Sephadex G-50 chromatography extracts of hypothalamic, midbrain, UBG and thyroid gland gave an immunoreactive peak which co-eluted with synthetic salmon CT. However, on HPLC the material in pigeon hypothalamus, midbrain, UBG and thyroid gland eluted in an identical manner when compared to each other but the major peak was 2 ml after that of synthetic salmon CT. These results clearly show that a salmon CT-like immunoreactive molecule is present in pigeon hypothalamus and midbrain, in addition to its main locations in the UBG and thyroid gland.