A Study on Prostate Inflammation in SD Rats After Castration Under the Effect of Estrogen/androgen at Different Concentrations
Authors: Wang Bo , Tian Ye , Ban Yong , Wang Zhen , Yang Bing , Pan Di , Luo Guangheng , Sun Zhaolin 
Published: January 2021

Abstract
Background: To clarify the expression of histological inflammation and major inflammatory factors in prostate of castrated rats induced by different concentrations estrogen/ androgen. Methods: Male Sprague-Dawley (SD) rats aged 3-4 months were randomly divided into the blank group (sham operation group, bilateral testicular specimens were retained), and the castration group (surgical removal of bilateral testes) and different concentrations of estrogen/androgen treatment after castration. Dihydrotestosterone (DHT) and estradiol (E) were administered daily by subcutaneous injection for one month, and the rats in each group were sacrificed by neck-broken method after one month. Obtained prostate specimens by surgery, and performed routine paraffin embedding and sectioning of prostate tissue. Observed the changes of prostate tissue structure and prostate inflammation under light microscope after Hematoxylin-eosin (HE) staining. Immunohistochemical method was used to detect the expression of TGF-β1, IL-6 and IL-8 in the rats prostate tissues. Results: After castration, when the exogenous E concentration was constant, the exogenous DHT(0-0.15mg/kg) concentration of SD rats in each group increased gradually, and the anatomical position score of inflammatory cell infiltration in each group of rats gradually increased. Further, even if the DHT concentration increased again after the exogenous DHT concentration reached at 0.5mg/kg, the score did not increase but decreased insteadly. From the area of tissues involved in inflammatory cell infiltration and the density of typical inflammatory cells, the inflammation score of each group of rats increased gradually with the increase of DHT concentration. When the exogenous DHT concentration was constant, from the anatomical location and the area of tissues involved in inflammatory cell infiltration in each group of SD rats, the inflammation score of each group of rats increased gradually with the increase of exogenous E concentration. The results of the immunohistochemical reaction showed that the positive rates of TGF-β1, IL-6 and IL-8 in SD rats after castration were higher than those in the blank group, and the positive rate of TGF-β1 was statistically significant compared with the blank group (P<0.05). When the concentration of exogenous E was constant, the positive rates of TGF-β1 and IL-8 in each group of DHT0.015-0.5mg/kg increased with the increase of the concentration of exogenous DHT. However, even if the exogenous DHT concentration increased again after the exogenous DHT concentration exceeded 0.5mg/kg, the positive rates of TGF-β1 and IL-8 in the E0.05+DHT1.5 group did not increase with the further increase of exogenous DHT, but decreased to a certain extent. In addition, when the exogenous DHT concentration was constant, the exogenous E concentration was gradually increased, and the positive rates of TGF-β1, IL-6 and IL-8 in SD rats in each group increased to some extent with the increase of exogenous E concentration. Conclusions: Sex hormone levels are involved in the regulation of prostate inflammation in SD rats. Different levels of estrogen and androgen have different levels of inflammatory response to prostate inflammation and the expression of TGF-β1, IL-6, IL-8 in castrated SD rats, and the positive expression of TGF-β1, IL-6, IL-8 can reflect the inflammation of prostate tissue in SD rats to a certain extent. In addition, there may be an inflection point between the ratio of estrogen/ androgen and prostate inflammation. After crossing this inflection point, the inflammation of the prostate did not further deepen even if the concentration of exogenous androgens increased again. Of course, it needs to be confirmed by more systematic and comprehensive experiments in vivo and vitro.