MH immunostaining in oocytes (all follicular stages) and primordial follicles. During postnatal development in mammals, the signal is virtually null in primordial follicles and is first observed in young growing follicles. The strongest signal appears in preantral and modest antral follicles and disappears quickly with growing follicle size. Staining is least intense through ovulation or at follicular atresia [46,49]. The localization of AMH in GlyT1 Inhibitor medchemexpress mammals agrees with its well-known role as an inhibitor of the activation of primordial follicles [18], despite the fact that in 1 study involving in vitro experiments it was observed that AMH elevated the proportion of increasing follicles [50], suggesting that AMH could activate folliculogenesis and steroidogenesis, in line with that observed in this function with sea bass. In teleosts, alternatively, the web pages of amh expression in the ovary differ significantly among species, as well as the localization of Amh protein by immunostaining has been described only in black porgy [42], orange-spotted grouper [51], Nile tilapia [35] and, in the present study, in sea bass. As observed in mammals, there is some controversy around the expression pattern of amh in germ cells, with reports on the presence of transcripts inside the oocytes of developing follicles in zebrafish ovaries [52]. In our prior function in sea bass [30], amh expression levels inside the entire ovary improved in the course of vitellogenesis and have been maximum in maturation and ovulation. On the other hand, when analyzing in the present study amh expression in isolated follicular cells, amh expression decreased in maturation, soon after the vitellogenesis stage, Kainate Receptor Antagonist medchemexpress meaning that the higher expression levels previously reported through maturation-ovulation would correspond to mRNA molecules present inside the oocyte. Even though amh expression may not be restricted for the somatic cells in fish, follicular cells seem to become the main source of amh expression within the ovaries of most fish species, as observed in other vertebrates. Research applying in situ hybridization in zebrafish and medaka show that amh is expressed in granulosa cells of previtellogenic and vitellogenic oocytes [20,23]. Within the hybrid fish Squalius alburnoides, amh can also be expressed in the adult ovaries, much more specifically within the follicular cells surrounding the primordial and key oocytes [29]. By contrast, in Japanese flounder amh is male-specific through each sex differentiation and adult life, and no expression is observed inside the ovary [24]. Even though amh is already expressed in principal and previtellogenic oocytes, the presence of Amh protein in the ovary just isn’t detected until the entry of vitellogenesis, as observed in black porgy [42], orange-spotted grouper [51], and within this operate, together with the exception of Nile tilapia, in whichInt. J. Mol. Sci. 2021, 22,ten ofit is found within the main growth stage but not for the duration of vitellogenesis [35]. Localization of Amh inside the adult ovary indicates that this growth element has a vital role through ovarian improvement, as observed in mammals, while its particular functions are nonetheless not identified and, probably, might differ depending on the species. In rodents and humans, AMHR2 colocalizes with AMH, mostly in the granulosa cells of preantral and modest antral follicles, with almost no expression in massive antral follicles and corpus luteum [3,10]. Having said that, AMHR2 expression was also observed in theca cells of preantral and smaller antral follicles in adult rats and human ovaries, but, unlike the granulosa cell express
