Activin Expression in the Testis: Exploring Its Critical Relationship with Seminal Fluid Composition and Implications for Male Fertility in Rabbits

Abstract

Background: The activin family of dimeric peptide hormones is produced in the testis and is believed to play paracrine and autocrine roles in regulating steroidogenesis. The quality, effectiveness, and parameters of sperm can be affected by changes in estrogen and plasma levels in the blood. Objectives: This study aimed to evaluate the immunohistochemical activity of activin in testicular tissue and its association with spermatogenesis. Materials and Methods: The study was conducted at Al-Nahrain University / College of Medicine from January 2024 to March 2025, involving 20 adult male rabbits. Animals were examined to exclude unhealthy individuals and were euthanized via chloroform inhalation. We monitored their behavior and measured their weights both before and after the experiment. Testes were dissected, and seminal fluid was collected for analysis. Results: Comparison between the two groups (A, B) revealed statistically significant differences in   number and motility of sperm, the width of germ cells, and the density of Sertoli cells. Notably, activin expression and plasma levels were significantly higher in the B group compared to those in group A. Conclusions: The expression and levels of activin subunits correlate with sperm parameters. In this study, the impact of disruptions in activin activity throughout the spermatogenesis cycle can be observed, highlighting the essential role of activin in balancing and regulating quality parameters in seminiferous epithelial dynamics and its complex regulatory mechanisms. In this study, we highlight the multifaceted interactions of one of the complex free hormones and its role in hormonal regulation and sperm production efficiency. We also examine the profound biological effects of this hormone, both in excess and in deficiency, on male reproductive health.