Current perspectives on the androgen 5 alpha-dihydrotestosterone (DHT) and 5 alpha-reductases in teleost fishes and amphibians

Non‐canonical expression patterns and evolutionary rates of sex‐biased genes in a seasonal fish

“…Curiously and complementary to the cyp19a1a pattern, the expression of one srd5a paralog ( srd5a1 ), which encodes dihydrotestosterone‐producing enzymes, exhibited a female‐biased pattern in S. pyrenaicus . A similar result was reported for the fathead minnow, in which srd5a3 was enriched in ovaries (Martyniuk et al, ). Whether or not this change is related to sex maintenance is moot; however, the predominant androgen in teleost fish is 11‐ketotestoster (Borg, ), a steroid that is less abundant in female fish than testosterone (Lokman et al, ).…”

Effects of 5α-dihydrotestosterone on expression of genes related to steroidogenesis and spermatogenesis during the sex determination and differentiation periods of the pejerrey, Odontesthes bonariensis

“…Such a scenario, may explain the female related gene expression pattern at 6 wph with no male biased sex ratio at 0.1 μg 5α-DHT/g dose (Fernandino et al, 2008a(Fernandino et al, , 2008bKarube et al, 2007;Perez et al, 2012). This line of reasoning was also suggested by Marlatt et al (2013) and Martyniuk et al (2013) in order to explain the in vitro vitellogenin stimulation by 5α-DHT in the fathead minnow. At the highest 5α-DHT dose, the expression profile of the selected genes was not statistically different to those of the control group, but resembled the male expression pattern observed in this species, as characterized by a high hsd11b2/cyp19a1a ratio (Fernandino et al, 2008a(Fernandino et al, , 2013bKarube et al, 2007).…”

Differential ligand selectivity of androgen receptors α and β from Murray–Darling rainbowfish (Melanotaenia fluviatilis)

“…Concentration-response profiles and transactivation maxima in response to natural androgens differed slightly, which could be expected given that the LBDs of the two subtypes exhibit amino acid identities of around 70%. However, the relative potency of natural androgens was similar for ARa and ARb, and the observed similar potency of 11-KT and DHT in both subtypes is notable given the increasing recognition of a potential role for DHT as an androgen of physiological importance in teleost fish (Margiotta-Casaluci et al, 2013;Martyniuk et al, 2013). In contrast, the large differences in relative potency of the synthetic androgen, 17b-trenbolone, suggests that sequence divergence between AR subtypes in teleosts is sufficient to confer differences in ligand specificity.…”