Development of a system for measuring calcitonin in the stingray Dasyatis akajei (a cartilaginous fish): the possible involvement of stingray calcitonin in gonadal development

Document Type: Original Article

Authors

1 Department of Biology, Faculty of Science, University of Toyama, Gofuku, Toyama, 930-8555, Japan

2 Noto Marine Laboratory, Institute of Nature and Environmental Technology, Division of Marine Environmental Studies, Kanazawa University, Noto-cho, Ishikawa, 927-0553, Japan

3 Department of Biology, College of Liberal Arts and Sciences, Tokyo Medical and Dental University, Ichikawa, Chiba, 272-0827, Japan

4 Peptide Institute, Inc, Ibaraki, Osaka, 567-0085, Japan

5 Life Science Research Center, University of Toyama, Sugitani, Toyama, 930-0194, Japan

6 Noto Center for Fisheries Science and Technology, Kanazawa University, Noto-cho, Ishikawa, 927-0552, Japan

7 Department of Zoology, D.D.U. Gorakhpur University, Gorakhpur, 273-009, India

8 College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Vietnam

9 Fisheries Technology Program, Faculty of Science and Technology, Prince of Songkla University, Pattani, 94000, Thailand

10.1007/s40071-019-00236-0

Abstract

To elucidate the physiological role of calcitonin (CT) in stingrays (cartilaginous fish), an enzyme-linked immunosorbent assay (ELISA) system using a specific antibody against stingray CT has been developed. Synthetic stingray CT was subcutaneously injected into mice four times—once every 2 weeks—together with an adjuvant. We purified the IgG antibody fraction using the protein A affinity chromatography from collected antiserum. Evaluating the antibody titer, we found the antibody’s optimum dilution ratio to be 600 times. Competitive ELISA has been developed using the antibody diluted 600 times. Our antibody did not cross-react with teleost CTs and muscle extraction, but cross-reacted with stingray plasma and the extract of the ultimobranchial gland, the secretary organ of stingray CT. Using this ELISA, we measured the plasma CT level in stingrays and examined its correlation with several mineral concentrations. Plasma CT did not show significant correlation to calcium, magnesium, inorganic phosphorus, sodium, chlorine, or urea, although there was a correlation among the factors involved in osmoregulation, such as sodium, chlorine, and urea. On the other hand, plasma CT was significantly correlated to body weight and length. Furthermore, there was a significant correlation between plasma CT and gonad weight. Since plasma CT was correlated with the weight of liver, which is involved in the synthesis of egg yolk protein, we examined the influence of 17β-estradiol (E2) on CT secretion. After E2 injection, the plasma CT level increased significantly. This is the first study to demonstrate that E2 induced plasma CT secretion in cartilaginous fish.

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