Comparative histomorphological characteristics of the endometrium of young and aged mares in estrus and diestrus

Abstract

The histomorphometric indices (height of the lining (LE) and glandular (GE) epithelium, diameters and density of glands) in endometrial samples (n=21) of young gynecologically healthy mares of 3–8 yo (n = 4) and older problem mares of 12–19 yo (n=7) were studied in estrus and diestrus of one cycle. The height of the LE and GE in aged mares was slightly higher than in young ones, but the difference was not significant. It was found significant differences between groups in diameters and density of glands, more obvious in stratum spongiozum (SS) then in stratum compactum (SC) of endometrium. It has been shown that diameter of endometrial glands in older mares was two to three times larger than in young mares in both estrus (55.9-22.5 μm, p<0.05) and diestrus (62.5-20.1 μm, p <0.01), respectively. The density of glands in SS in young mares in diestrus significantly (p<0.01) increased, compared with this in estrus (9.8-17.5 units/field), while in older mares it almost did not change (11.1-11.3 units/field). The difference of histomorphometric indices in estrus and diestrus can serve as indirect characteristic of an elasticity of an endometrial tissue probably connected with clearance of the uterus. Therefore the double biopsy carried out in estrus and diestrus can be useful for endometrium function assessment in mares.