Immunohistochemical and histochemical identification of proteins and carbohydrates in the equine endometrium: Reaction patterns in the cycling mare

Little is known about the stage of estrus cycle-dependent variations of uterine secretions of the more and most published results were based on evaluation of uterine flushings. Hence, the aim of this study was to define patterns of expression of different endometrial proteins throughout the estrus cycle using newly established immunohistochemical methods and endometrial biopsies. Therefore, endometrial biopsies were collected from three mares on defined days of the estrus cycle with known concentrations of estradiol and progesterone in serum. The proteins uteroglobin, uteroferrin, calbindin(D9k) and uterocalin were examined using polyclonal antibodies. Furthermore glycogen was identified using the PAS-reaction prior to and after a-amylase digestion. During the estrus cycle expression of the examined proteins, as well as glycogen, revealed a typical, progesterone-dependent pattern. In the early- and mid-interestrus there is a simultaneous increase in expression of uterocalin and glycogen staining intensity associated with increasing concentrations of progesterone in peripheral blood. The maximal expression of calbindin(D9k) was also in association with high levels of circulating progesterone in mid-interestrus. In contrast, secretion of both uteroglobin and uteroferrin was simultaneously associated with the decrease in circulating concentrations of progesterone in mid-to late-interestrus. However, it has to be emphasized that distinct among mare differences were obvious. This new method enables pathologists to interpret changes in the uterine secretion pattern associated with fertility reducing diseases by using a single endometrial biopsy