Studies on the hypocalcemic actions of salmon calcitonin and ultimobranchial gland extracts in the freshwater teleost Cyprinus carpio.

A single injection of synthetic salmon calcitonin (sCT) or homologous ultimobranchial gland (UBG) extract caused a significant reduction in total and ultrafiltrable plasma Ca2+ in a freshwater teleost, Cyprinus carpio. A time-bound analysis on the effect of sCT or UBG extract caused a short-duration hypocalcemia and the response was more pronounced in fish kept in low-Ca2+ water. Sexually immature fish showed a greater response than did mature fish. In all the studies the protein-bound Ca2+ fraction remained unaffected. The observation thus indicate a potent hypocalcemic role of calcitonin or UBG in freshwater common carp under laboratory conditions.