Primary Structure and Bioactivity of Bullfrog Calcitonin

Abstract Calcitonin was isolated from the bullfrog, Rana catesbeiana, and the first amino acid sequence of an amphibian calcitonin was determined to be Cys-Ser-Gly-Leu-Ser-Thr-Cys-Ala-Leu-Met-Lys-Leu-Ser-Gln-Asp-Leu-His-Arg-Phe-Asn-Ser-Tyr-Pro-Arg-Thr-Asn-Val-Gly-Ala-Gly-Thr-Pro-NH 2 . Some portions of this sequence are specific to bullfrog calcitonin, and other portions are similar both to teleost calcitonins and to mammalian calcitonins. Administration of 5 pmol of bullfrog calcitonin to rats revealed a hypocalcemic potency similar to that of salmon calcitonin, at least for the first 3 hr.