Histomorphometric and Histochemical Changes in the Mare Tuba Uterina During the Oestrous Cycle and Follicular Cyst...

This study evaluated histomorphometric and histochemical changes in the mare tuba uterina during different reproductive stages and under follicular cyst conditions. Forty nonpregnant mares were classified into follicular, luteal, post-ovulation and follicular cyst groups (n = 10/group). Histological evaluation of the isthmus, ampulla and infundibulum was performed using haematoxylin and eosin staining, while periodic acid-Schiff (PAS) staining was used to assess epithelial secretory activity. Morphometric parameters included number of primary mucosal folds, fold length, epithelial height and fold thickness. Descriptive observations indicated that the infundibulum possessed the most elaborate mucosal architecture, whereas the isthmus exhibited the simplest organization. Comparisons among reproductive stages were performed separately within each oviductal region. Across all oviductal regions, the follicular phase demonstrated the highest morphometric values, characterized by increased fold number, epithelial height and fold dimensions (p < 0.05). In contrast, most morphometric parameters decreased during the luteal and post-ovulation stages. For most variables, post-ovulation values remained higher than those observed during the luteal phase. The ampulla exhibited the strongest PAS reactivity during the luteal phase, with abundant apical PAS-positive granules indicating enhanced epithelial secretory activity, whereas moderate staining was observed during the follicular phase. Mares with follicular cysts showed the lowest morphometric values in all oviductal regions and weak, irregular PAS reactivity. These findings demonstrate that the mare tuba uterina undergoes pronounced cyclical remodelling influenced by ovarian status. Follicular cysts were associated with altered histological and secretory characteristics of the oviduct, which may compromise the physiological environment required for normal reproductive function.