Abstract
The effect of the administration of various steroid hormones on the breakdown of myofibrillar proteins and collagen was examined in association with some protease activities to specify the protease implicated in the breakdown of these proteins. The administration of estradiol-17β remarkably increased the content of free 3-methylhistidine (3-MeHis), a specific constituent of myofibrillar proteins, in female fish, but decreased it in male fish. Administration of an androgen, testosterone, increased the free 3-MeHis contents both in male and female fish. Cathepsin L activity assayed as a hydrolyzing activity on benzyloxycarbonyl-Phe-Arg-7-(4-methyl)coumaryl-amide was correlated with the change in the free 3-MeHis content induced by hormone administration in the case of female fish. Although not significantly, testosterone showed increasing effects on the content of free hydroxyproline, a specific constituent of collagen, in male and female fish, respectively. The result suggested that these hormones promoted the breakdown of collagen. However, the induction of a specific protease correlated with the collagen breakdown was not detected in the present study.
