Dietary metyrapone blocks cortisol synthesis in pacu, Piaractus mesopotamicus (Holmberg, 1887), stressed by air exposure

Tested was the efficiency of dietary metyrapone (MTP) in the inhibition of cortisol biosynthesis, as a tool to elucidate the effects of this hormone in the tropical fish pacu (Piaractus mesopotamicus H.) during air-exposure-induced stress. Moreover, MTP efficiency was shown to be affected by both the dose and time of administration and that a daily dose of 30 mg kg(-1) body weight for 10 days reduced the levels of circulating cortisol in stressed fish. The tested method of MTP administration, including the concentration and the time of administration, efficiently regulated cortisol synthesis in a non-invasive manner.