EFFECT OF STEROID-HORMONE ADMINISTRATION ON THE BREAKDOWN OF MUSCLE PROTEINS IN AYU

The effect of the administration of various steroid hormones on the br eakdown of myofibrillar proteins and collagen was examined in associat ion with some protease activities to specify the protease implicated i n the breakdown of these proteins. The administration of estradiol-17 beta remarkably increased the content of free 3-methylhistidine (3-MeH is), a specific constituent of myofibrillar proteins, in female fish, but decreased it in male fish. Administration of an androgen, testoste rone, increased the free 3-MeHis contents both in male and female fish . Cathepsin L activity assayed as a hydrolyzing activity on nzyloxycar bonyl-Phe-Arg-7-(4-methyl)coumaryl-amide was correlated with the chang e 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 c onstituent of collagen, in male and female fish, respectively. The res ult suggested that these hormones promoted the breakdown of collagen. However, the induction of a specific protease correlated with the coll agen breakdown was not detected in the present study.