Recently, Dehydroepiandrosterone (DHEA), a steroid previously believed to function solely as a pro-hormone, has been utilized to measure chronic stress levels in humans. DHEA is abundant in primates but found in lower concentrations in rodents and other animals. In mammals, DHEA is produced in steroidogenic tissues and the nervous system from pregnenolone, the same precursor used to synthesize cortisol, through the Δ5 pathway. DHEA profile differs among species and varies according to the different physiological status, and although limited information is available regarding non-mammalian species, recent research has demonstrated that DHEA is present and detectable in teleost scales and appears to be correlated with chronic stress exposure. This study is focused on evaluating the gonad DHEA profile associated with a teleost species, Rainbow trout, as a potential synthesis site and the correlations with other biological matrices.Sampling was carried out in a commercial freshwater fish farm and trout were sampled based on sex, and sexual maturity. Furthermore, half of the fish from each group were subjected to acute stress conditions through overcrowding for thirty minutes. Trout were thus divided into 8 different groups based on the combinations of physiological conditions: sex (male or female), sexual maturity (mature or immature), and stress application (control and stress), with 12 animals per group (Total n = 96; 1182.1 g ± 263.4).
For cortisol and DHEA analysis, an adapted specific microtiter radioimmunoassay (RIA) was used to measure the hormone levels.
Despite acute stress appeared to not cause a DHEA profile modification, an higher level has been observed in females than in males in all the matrices besides the gonads, where males showed higher levels than females (Fig. 1). Sexual differentiation has been shown, even differently, for other species such dogs, killer whales and rhesus monkeys and the European starling. Moreover, in our study, gonads level showed an interesting pattern (Fig. 2), with immature males presenting an higher level of DHEA if compared to all the other groups, suggesting a potential participation of this hormone in maturation processes and identifying testis of pre-puberty specimens as potential sites of its synthesis.