The androgen receptor (AR) plays a key role in reproduction, and aromatase (P450arom), nuclear oestrogen receptors (ERs) α and β, and G protein‐coupled receptor 30 (GPR30) are important for testicular and epididymal cell proliferation and development. In the study, we have investigated the expression and localization of AR, P450arom, ERα, ERβ and GPR30 in testes and epididymides of sexually mature sheep by quantitative reverse transcription–polymerase chain reaction, Western blotting and immunohistochemistry. The results demonstrate that the AR, P450arom and ERα levels in the caput and corpus epididymis were significantly lower than those in the testis and cauda epididymis (p < .05), the ERβ level in the testis was significantly higher than in the caput, corpus and cauda epididymis (p < .05), and the GPR30 level in the caput epididymis was significantly lower than in the testis and corpus and cauda epididymis (p < .05). These receptors were mainly detected in epididymal epithelial, basal, smooth muscle, Sertoli and Leydig cells, as well as in spermatozoa. Taken together, the results suggest that sheep epididymides and testes have the potential for estradiol synthesis and are the targets of both androgens and estradiol. These results provide a foundation for further studies on the mechanisms of androgens and estradiol signalling in the testes and epididymides of sheep.
The demand for economic benefits has led to an increase in the proportion of high-concentrate (HC) feed in the ruminant diet, resulting in an increased incidence of subacute ruminal acidosis (SARA). During SARA, a high concentration of lipopolysaccharide (LPS) translocated in the rumen induces a systemic inflammatory response. Inflammatory diseases, such as endometritis and mastitis, are often associated with SARA; however, in sheep, the mechanism of the effect of SARA on the endometrium has rarely been reported. Therefore, the aim of this study was to investigate, for the first time, the influence of LPS translocation on endometrial tight junctions (TJs) during SARA in sheep. The results showed that LPS and TNFα levels in the ruminal fluid, serum, and endometrial tissue supernatant during SARA increased, transcription levels of TLR4, NFκB, and TNFα in the endometrium increased, the protein expression level of claudin-1 in the endometrium increased, and the protein expression level of occludin decreased. 17β-estradiol (E2) inhibits claudin-1 protein expression and promotes occludin expression, and progesterone (P4) promotes claudin-1 protein expression and inhibits occludin protein expression. E2 and P4 regulate claudin-1 and occludin protein expression through their receptor pathways. Here, we found that LPS hindered the regulatory effect of E2 and P4 on endometrial TJs by inhibiting their receptor expression. The results of this study indicate that HC feeding can cause SARA-induced LPS translocation in sheep, increase susceptibility to systemic inflammation, induce the endometrial inflammatory response, and cause endometrial epithelial TJ damage directly and/or by obstructing E2 and P4 function. LPS translocation caused by SARA has also been suggested to induce an endometrial inflammatory response, resulting in endometrial epithelial barrier damage and physiological dysfunction, which seriously affects ruminant production. Therefore, this study provides new evidence that SARA is a potential factor that induces systemic inflammation in ruminants. It provides theoretical support for research on the prevention of endometritis in ruminants.
Steroid hormones and receptors play important roles in female reproduction, and their expression patterns affect follicular growth and development. To examine the expression of dihydrotestosterone (DHT) synthases (5α‐reductases (5α‐red1 and 5α‐red2)) and androgen receptor (AR) during follicular development, and the regulation of DHT signalling by follicle‐stimulating hormone (FSH) and luteinizing hormone (LH), we have used enzyme‐linked immunosorbent assays, quantitative real‐time polymerase chain reaction, immunohistochemical staining and Western blotting to examine DHT synthesis in small (≤2 mm), medium (2–5 mm) and large (≥5 mm) sheep follicles. Expression of 5α‐red1, 5α‐red2 and AR was observed in ovine ovaries, and with the development of follicles, the expressions of 5α‐red1 and 5α‐red2 mRNA and protein increased, but the levels of AR mRNA, protein and DHT level decreased. In addition, granulosa cells were treated with FSH (0.01, 0.1 and 1 international unit (IU)/ml), LH (0.01, 0.1 and 1 IU/ml) and testosterone (T, 10–7 M) to evaluate the effects of FSH and LH on DHT and oestradiol (E2) synthesis and 5α‐red1, 5α‐red2 and AR expression. We found that FSH and LH upregulated 5α‐red1 and 5α‐red2 in sheep granulosa cells, but downregulated the concentration of DHT and expression of AR. Meanwhile, FSH and LH significantly upregulated the expression of aromatase (P450arom) and secretion of E2. This result indicates that although FSH and LH promote the expression of 5α‐red1 and 5α‐red2, T is not transformed into DHT, but E2. This study reveals the reason why DHT concentration is downregulated in large follicles and lays a foundation for further exploring the synthesis mechanism of DHT during follicular development.
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