Seasonal adaptations in the ultrastructural and immunohistochemical characterization of the epididymal duct in Meriz bucks.

BACKGROUND

Although the epididymal duct (ED) supports sperm maturation and storage, its ultrastructural and immunohistochemical adaptations in seasonal breeders, such as the Meriz buck, remain unclear.

AIM: This study aimed to investigate seasonal adaptations in the ultrastructure and immunohistochemical profile of the ED in Meriz buck during mating and non-mating seasons.

METHODS

Twenty-four Meriz bucks from Duhok Province, Iraq, at the College of Veterinary Medicine were restudied. Epididymal tissues were examined using Transmission Electron Microscopy and immunohistochemistry α-smooth muscle actin (α-SMA), S-100, and von Willebrand factor (VWF) to characterize cellular localization during the mating and non-mating seasons.

RESULTS

The epithelium of the ED comprised principal cells (PCs), basal cells, apical cells, narrow cells (NCs), and clear cells. Ultrastructurally, PCs displayed Abundant microvilli, apical blebs, and well-developed endocytotic apparatuses (vesicles and multivesicular bodies), which were more prominent in autumn (October) than in other seasons. Adjacent PCs were joined by occluding junctions, forming the Blood-Epididymal Barrier. During autumn, the supranuclear region of PCs exhibited a larger Golgi apparatus, extensive rough endoplasmic reticulum, and numerous mitochondria, whereas other epithelial cells exhibited notable seasonal variations. Immunohistochemical, α-SMA expression intensified in the peritubular and vascular smooth muscle layers during autumn (9.3 ± 0.01, p < 0.01), suggesting enhanced contractile activity or smooth muscle remodeling associated with reproductive seasonality. S-100 immunoreactivity was strongest in the PCs and NCs (7.5 ± 0.002, p < 0.01), whereas VWF expression in vascular endothelial cells increased significantly in autumn compared to other seasons (0.99 ± 0.01, p < 0.01).

CONCLUSION

The study concludes that in October, increased ultrastructural activity and elevated expression of α- SMA, S-100, and VWF in the ED indicate increased reproductive function. Suggesting that this period corresponds to the Meriz bucks' mating season.