Progestin is important for testicular development of male turbot (Scophthalmus maximus) during the annual reproductive cycle through functionally distinct progestin receptors

Abstract

In teleost, sex steroid hormones are critical for reproduction. Progestin is known to promote spermiation. To further understand the functions of progestin via its receptors during the annual reproductive cycle in male turbot (Scophthalmus maximus), we observed testicular development, quantified several sex steroid hormones, detected the expression of progestin receptors, and measured various sperm parameters. Results showed that the turbot testicular structure was of the lobular type. During breeding season, a number of spermatocytes (stage III) developed into spermatids (stage IV), then differentiated into sperm during spermiogenesis (stage V), and finally regressed to spermatocytes (stage VI). Concomitant with testicular development, serum progesterone (P4) and 17α,20β-dihydroxy-4-pregnen-3-one (DHP) exhibited higher levels from stage IV to V than other stages. Furthermore, males with higher motility sperm showed higher levels of P4 and DHP compared with fish with lower motility sperm. These results indicated that P4 and DHP might induce spermatogenesis due to seasonal changes. Concurrently, in testes, the nuclear progesterone receptor (pgr) was expressed throughout the reproductive cycle and its level peaked during spermiogenesis while expression of membrane progestin receptor alpha (mPRα) did not change significantly. However, in sperm, mPRα expression was higher than in testes and had a significant positive correlation with curvilinear velocities (VCL), sperm motility, and motility duration. In conclusion, progestin appears to exert a direct pgr-mediated effect on spermiogenesis and improve sperm motility characteristics depending on the abundance of mPRα protein in sperm during spermiation.

The ultrastructure of spermatogenic cells and morphological evaluation of testicular development in the silver pomfret (Pampus argenteus)

“…In teleost, the testes have two types of seminiferous tubules: lobular and tubular (Feng et al, 2017;Schulz et al, 2010). In this study, P. argenteus had an anastomosing tubular testis, with the germinal compartments converging towards the spermatic duct in the periphery, and the spermatogenesis had a cystic arrangement (Figure 5).…”

Effects of acute and chronic zinc exposure on steroid hormone receptor expression in the lined seahorse, Hippocampus erectus

“…Therefore, high expression levels of ER and AR in the liver may be associated with hormone activity related to hepatic lipid metabolism regulation. PR has been shown to produce more pronounced tissue‐specific expression divergence among species: consistent with its different functions in both male and female reproduction (Aizen et al, ; Fang et al, ; Feng et al, ; Yong et al, ), PR showed substantial variation of expression between genders, for example, testis‐specific expression in zebrafish (Chen et al, ) and expression unique to the ovaries in half smooth tongue sole, Cynoglossus semilaevis (Shi, ). Sexually unbiased expression patterns and wide distribution of PR in various tissues in the lined seahorse may indicate functions that differ from other bony fishes.…”

A Deep Insight of Spermatogenesis and Hormone Levels of Aqua-Cultured Turbot (Scophthalmus maximus)

“…An aliquot of 1 µL semen was activated with 100 µL seawater (pH 7.1) containing 0.1% bovine serum albumin (BSA). Sperm motility was defined as the percentage of moving spermatozoa with a VCL > 45 µm/s at 15 s after sperm activation (Feng et al, 2018). The sperm deformity ratio of each sample was calculated by TEM images.…”

“…The germ cells and early gonadal development during sex differentiation were examined by using histological sections (Zhao et al, 2017). The characteristic of progestin and its receptors during the annual reproductive cycle of male turbot were studied (Feng et al, 2018). The function of vitamin E in stimulating the expression of gonadotropin hormones in the pituitary in vitro was reported (Huang et al, 2019).…”