Seasonal changes in 11-ketotestosterone and relative ventricle mass in wild rainbow trout, Oncorhynchus mykiss

Abstract

To test the hypothesis that 11-ketotestosterone (KT) stimulates cardiac hypertrophy in maturing male rainbow trout, the plasma levels of 11-KT and ventricle mass were measured in a wild stock of trout from the Tongariro river system in New Zealand over a 12-month period. The peak levels of 11 -KT in the males, 102.3 20.1 ng ml−1 occurred in July-August. The plasma levels of 11-KT did not change significantly over the year in females. The ventricle mass of males (adjusted for body mass) was 18% larger than that of females. The results of this study are consistent with the hypothesis that 11-KT is one factor which stimulates cardiac hypertrophy in maturing males. However, other factors, such as activity associated with reproduction, also appear to be important in inducing the increase in ventricle mass of males. © 1996, Copyright Taylor & Francis Group, LLC.