Although further studies are needed, the existence of several variants of ARs in fish leukocytes, together with the affinity of all the androgens previously described to ARs, may lead to an array of different sensitivities in the cells to different androgen levels

Although further studies are needed, the existence of several variants of ARs in fish leukocytes, together with the affinity of all the androgens previously described to ARs, may lead to an array of different sensitivities in the cells to different androgen levels. 4. of this manuscript is to review our present knowledge concerning the effect of sex steroid hormones and the presence of their receptors on fish leukocytes, taking into consideration that this studies performed vary as regard the fish species, doses, exposure protocols and hormones used. Moreover, we also include evidence of the probable role of progestins in the regulation of SU 3327 the immune system of fish. (tnf) transcriptional levels and the IL1 content in serum. However, these effects were not constant with time [76]. Interestingly, chronic exposure to E2 during embryonic development, hatching and early larval development of rainbow trout hSPRY2 fry prospects to an impairment of the match activation pathway upon a bacterial challenge and a concomitant decrease in the survival rate of the population exposed to E2 compared to nonexposed groups [77]. When the adaptive immune response is analyzed, species-dependent effects were also observed. Regarding total levels of IgM, they fell upon E2 treatment in gilthead seabream and rainbow trout ([62,95]. A tissue-specific SU 3327 pattern of expression in fish immune tissues has been observed for nuclear ESRs (Table 2). In channel catfish, ESR1 is usually expressed in spleen, blood and head kidney, while ESR2 is only expressed SU 3327 in spleen [96]. ESR2 is usually expressed in the spleen and head kidney of common single (L.) the activation of an immune response upon -glucan exposure decreased the serum levels of T that was predicted by the immunocompetence-handicap hypothesis [92]. However, T did not suppress the SU 3327 lysozyme activity of plasma or the production of ROIs by blood leukocytes and head kidney phagocytes [92] as also occurs with the phagocytic activity of peripheral blood of tilapia and common carp when treated in vitro with T [68]. In fact, in common carp, T has tissue-dependent effects on leukocytes as it sharply reduced the number of IgM secreting cells and IgM production in splenic leukocytes but not in circulating blood and head kidney leukocytes [81]. Surprisingly, the innate immune system of gilthead seabream is usually stimulated by T. Thus, in vivo an increase of serum T levels brought on high match and peroxidase activity levels [78]. T also primed the phagocytosis and ROIs production activities of head kidney leukocytes in vitro [91] and in vivo [90]. In fact, the transcription levels of interleukin 1, and some genes are up-regulated in T-exposed head kidney leukocytes in vivo [90], as also occurred when professional phagocytic cells were isolated and treated with T in vitro [91]. 3.2. 11-Ketotestosterone As 11KT is the main androgen in fish, most studies into androgen regulation of the immune response have used this androgen. In rainbow trout, 11KT triggers the same effect as T, decreasing the number and capability of IgM-secreting cells of spleen, head kidney, blood and skin [79]. ROIs production and the phagocytic activity of common carp head kidney macrophages also decreased by 11KT [70]. However, when peripheral blood phagocytic activity after 11KT exposure was analysed, no effects were observed in common carp or tilapia [68], nor in the apoptotic rate of splenic or peripheral blood leukocytes of common carp [123]. In gilthead seabream, 11KT is able to increase proIL-1 accumulation and the ROIs production activity of non-stimulated head kidney phagocytes [67]. However, 11KT impairs the activation of the ROIs production by total head kidney leukocytes upon challenge with bacterial DNA in vitro [91]. Moreover, acidophilic granulocytes and macrophages of gilthead seabream did not respond equally to 11KT. Thus, 11KT was quite effective at decreasing the gene expression of several in isolated acidophilic granulocytes activated or not with bacterial DNA, while in activated or non-activated macrophages the expression of and increased in a dose-dependent manner at most of the doses used [91]. Interestingly, when macrophages are treated with T and 11KT simultaneously, T inhibits the up-regulation of and genes induced by 11KT [91]. In male three-spined sticklebacks ( em Gasterosteus aculeatus /em ), a negative correlation between 11KT serum levels and ROIs production in the phagocytosis assay was observed [94]. 3.3. Other C-19 Steroid with Androgenic Function In fish, DHT and OHT are also produced from T and in some species, they are the main androgens found in plasma or testis. Thus, in urohaze goby ( em Glossogobius olivaceus /em ), the main androgen is usually DHT, which is usually produced by T conversion in several tissues including brain and gonad. Recent studies have exhibited SU 3327 that DHT has androgenic functions in juvenile fathead minnows ( em Pimephales promelas /em ) where it triggers testicular development.