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  • In the present study we first examined

    2021-04-20

    In the present study, we first examined the in vivo and ex vivo effects of androgens on ep1 Mechlorethamine HCl synthesis in the olfactory rosette of male B. sinensis. Thereafter, we cloned two different B.sinensis ar cDNAs and investigated their roles in the effects of 11-KT on ep1 expression.
    Material and methods
    Results
    Discussion It is well documented that androgens modify olfactory processing in vertebrates. For example, treatment of female mice with androgen on the day of birth is sufficient to produce the male-typical olfactory preference for female-soiled bedding [38]. It has been reported in several teleost species that androgens increase the olfactory sensitivity in response to prostaglandin pheromone [5,15], but the mechanism is still unclear. One possibility may be that androgens increase olfactory epithelium thickness as well as surface area, which results in higher density of OSNs for pheromone detection [39,40]. Besides the number of OSNs, the positions of OSNs within the olfactory epithelium change from deep to superficial throughout the year [41]. The androgen-induced reorganization of OSNs (density and position) might contribute to higher sensitivity to pheromones. Alternatively, androgens may directly bind to androgen receptors in the olfactory epithelium to modulate the expression of receptors for pheromones [20]. The finding in mice supports this hypothesis by showing that T modulates the expression of vomeronasal receptors, thus altering behavioral responses to pheromones [17]. In B. sinensis, mature fish displayed greater EOG response to sex pheromone PGE2 and higher olfactory ep1 transcript levels than immature fish [30,31]. Moreover, Ep1 protein was found in the dendritic knobs of OSNs in the olfactory epithelium, indicating Ep1 is a candidate receptor for pheromone PGE2. In the present study, we found that androgens up-regulated the expression of ep1 in the olfactory rosette of B. sinensis, suggesting that androgens increase the olfactory sensitivity to pheromone PGE2 by modulating the expression of ep1. Since the AR agonist R1881 also increased the expression of ep1, we suppose that the effects of androgens are mediated by Ar in B. sinensis. As found in many other teleost species, two Ar subtypes (Arα and Arβ) were identified in B. sinensis. It is supposed that Arα and Arβ might perform different functions, because of their differential tissue expression pattern, their differential transactivation properties and the low similarity of DBDs [25]. Similarly, characteristics for arα and arβ were observed in B. sinensis. The arα was dominantly expressed in the gill, intestine, muscle and skin, while the arβ was dominantly expressed in liver, testis and ovary. The DBDs of B. sinensis Arα and Arβ shared only 69% sequence similarity, the predicted α-helixes of Arα and Arβ that interacts with ARE showed one amino acid difference (Supplemental Fig. 2C), and Arα showed higher transactivating capacity via AREs than Arβ (Supplemental Fig. 4). Furthermore, B. sinensis Arα but not Arβ displayed constitutive nuclear localization, which is similar to previous reports in Murray–Darling rainbowfish (Melanotaenia fluviatilis), mosquitofish (Gambusia affinis) and medaka (Oryzias latipes) Arα [24,25]. These results suggest that B. sinensis Arα and Arβ might have clear distinct biological functions. In the olfactory rosette of B. sinensis, arα and arβ showed different expression levels and different expression patterns during spermatogenesis. The expression of arα transcripts was higher in mature than in immature males, which was similar to the expression change of ep1 transcripts [31]. In mature male fish, the expression of arα transcripts is about 4 times higher than that of arβ. Importantly, activated Arα, but not Arβ, transactivated ep1 promoter in HEK293T cell line. It is likely that Arα mediates androgen-induced up-regulation of ep1 in the olfactory rosette of B. sinensis. Although it is supposed that teleost Arα and Arβ might perform different functions, no clear evidence has been shown to support this hypothesis so far. The present study is the first to show the different functions of Ars in olfaction. It is also worth mentioning that arα was widely distributed in the olfactory epithelium, and many Ep1-negative OSNs also expressed arα, suggesting that androgen signaling might also regulate the responsiveness to other pheromones in male B. sinensis.