135 GLANDS IN THE OVIDUCTAL MUCOSA OF THE MARE

Abstract

The oviduct plays a key role in the reproductive process in mammals allowing transport, reservoir, and capacitation of sperm (Hunter RH 2008 Mol. Reprod. Dev. 75, 167-174), fertilization, and early embryo development among other events. The oviductal mucosa is organized in a vast net of folds that projects towards the lumen (Trautman A and Fiebiger J 1952 Comstock. Publ. Assoc., Ithaca, NY, USA). In a preliminary study, the presence of some glandular structures in the oviductal mucosa was noticed. Detailed histological studies have incredibly not been described in the mare. The objective of this work was to study the presence of glands in the mare’s oviduct. Mares, in good body condition, 3 to 14 years old, were selected at a local slaughterhouse. Reproductive status was determined by transrectal palpation and ultrasonography. Mares were selected in anovulatory phase (n = 8), in estrus (n = 7), at Day 1 to 2 post-ovulation (n = 6) and in diestrus at Day 7 to 8 post-ovulation (n = 7). Reproductive tracts were harvested immediately following slaughter and were placed on ice. Oviductal samples of 1.5 cm were taken from the ampulla, the ampullary-isthmic junction (AIJ), and the isthmus and placed in formalin for fixation and subsequent process for hematoxylin-eosin stain. The number of glands was counted at ×400 in 5 optical fields and was compared by non-parametric Kruskal-Wallis test. Glandular structures were observed in 100% of the oviducts. These glands were alveolar type and resembled those in the endometrium. The glands showed 2 locations: in the periphery of the mucosa (peripheral glands) and within the thickness of the mucosa folds. The peripheral glands were more abundant than those within the mucosa folds (P < 0.001). The amount of glands decreased progressively from the ampulla (5.7/5 fields) to the AIJ (4.5) to reach a minimum number in the isthmus (0.2; P < 0.05). For each oviductal region, the amount of glands did not change through the different reproductive stages (P > 0.05). The epithelium of these glands was formed by ciliated and non-ciliated epithelial cells arranged in a similar way of the epithelial surface. However, the peripheral glands were stained with lighter intensity than the epithelial cells in the mucosal surface. In all literature searched, which included several textbooks of veterinary histology, no reference to glands in the oviducts of several domestic species including the mare was found. In contrast, glands in the oviduct have been described in birds (Richardson KC 1935 Biol. Sci. 225, 149-195) where they produce albumen and the eggshell membranes, and interestingly, one article about the oviduct of the bitch (Steinhauer N et al. 2004 Reprod. Domest. Anim. 39, 110-119) showed evidence of glands in this organ. In the mare, these oviductal glands probably add a distinct secretion of the oviductal surface to the tubal fluid since they show different chromatic affinity. Further investigation is needed to understand the function of these glands in the mare oviductal physiology.