Calcitonin variations in male and female trout, Salmo gairdneri, during the annual cycle

Abstract

Calcitonin (CT) levels in the ultimobranchial body and in plasma were radioimmunoassayed in rainbow trout, Salmo gairdneri, as a function of the annual cycle. In male and female, there was an important increase in the CT levels in the ultimobranchial body and in plasma. These variations in CT levels in both male and female suggest that sexual maturity influences the synthesis and the secretion of calcitonin in fishes. A positive correlation was observed between plasma and ultimobranchial CT levels and the gonadosomatic index in both sexes, suggesting that CT has a role in the processes involved in gonadal development.