New Calcitonin Isolated from the Ray, Dasyatis akajei

Calcitonin causes hypocalcemia by inhibiting the resorption of calcium from the bone in mammals. Calcitonin has now been isolated from the ultimobran- chial gland of a cartilaginous fish, the ray (Dasyatis akajei), and its amino acid has been determined to be H-Cys-Thr- Ser-Leu-Ser-Thr-Cys-Val-Val-Gly-Lys-Ser-Gln-Gln-Leu- His-Lys-Leu-Gln-Asn-Ile-Gln-Arg-Thr-Asp-Val-Gly-Ala- Ala-Thr-Pro-NH=. Although its basic structure is well conserved, the amino acid sequence of ray calcitonin is considerably different from that of other calcitonins se- quenced to date. Because the ray lacks calcified bones, an examination of the effect of calcitonin in this fish may elucidate a new role for calcitonin in vertebrates.