New Calcitonin Isolated from the Ray, Dasyatis akajei.

Area of Science:

• Comparative endocrinology
• Fish physiology
• Molecular biology

Background:

• Calcitonin is a hormone known to regulate calcium levels in mammals by inhibiting bone resorption.
• The ultimobranchial gland is a key endocrine organ in fish, homologous to the thyroid C-cells in mammals, and produces calcitonin.

Purpose of the Study:

• To isolate and characterize calcitonin from the cartilaginous fish, Dasyatis akajei (ray).
• To determine the amino acid sequence of ray calcitonin.
• To explore potential novel roles of calcitonin in vertebrates, especially in species lacking calcified bones.

Main Methods:

• Isolation of calcitonin from the ultimobranchial gland of the ray.
• Amino acid sequencing of the isolated calcitonin using established biochemical techniques.

Main Results:

• Calcitonin was successfully isolated from the ray's ultimobranchial gland.
• The complete amino acid sequence of ray calcitonin was determined: 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-NH2.
• Ray calcitonin exhibits significant sequence divergence compared to mammalian and other fish calcitonins, despite conserved structural elements.

Conclusions:

• The unique amino acid sequence of ray calcitonin suggests evolutionary adaptations in its function.
• The absence of calcified bones in rays provides a unique model to investigate non-skeletal roles of calcitonin.
• Further studies on ray calcitonin may elucidate novel functions of this hormone in vertebrate physiology, beyond calcium homeostasis in bone.