Effects of salmon calcitonin and anti-salmon calcitonin antibody on plasma calcium concentrations in the goldfish,Carassius auratus

The role of calcitonin (CT) in plasma calcium regulation was studied by the administration of exogenous CT and anti-salmon(s) CT antibody using goldfish,Carasius auratus, loaded or otherwise with calcium. CT elicited a decrease in plasma calcium concentrations at a dose of 10 ng/g body weight 1 h after administration. However, no effects were observed following doses of 30 ng and 50 ng/g 1 h, nor for the three doses 3 h after administration. In calcium-loaded fish, the effect of CT was different depending on the dosage of CT. Ten ng and 50 ng/g induced a decrease and an increase in plasma calcium concentrations, respectively, 3 h after administration. Anti-sCT antibody (0.02 μg or 0.1 μg/g) did not affect plasma calcium concentrations. In calcium-loaded fish, neither dose of anti-sCT antibody changed plasma calcium concentrations 1 h after administration. However, following a dose of 0.1 μg/g, plasma calcium concentrations decreased after 3 h. A positive correlation between plasma calcium concentrations and the gonad somatic index (GSI) in females was no longer apparent after administration of anti-sCT antibody. There was no relationship between plasma calcium concentrations and GSI in control and anti-sCT antibody-treated males. These results suggested that CT regulates plasma calcium concentrations in different ways depending on the dosage with CT having a role in calcium physiology during vitellogenesis.