This investigation examines the relationship between implantation strategy and gap junction protein expression in uterine endometrium. The pattern of gap junction and connexin protein expression was analyzed in porcine and equine endometrium from cycling and pregnant animals using electron microscopy and immunocytochemistry. Functional analysis of cellcell communication was also monitored by laser cytometry in primary cultures of endometrial epithelial cells. Gap junctions were detected in endometrial stroma of cycling and pregnant animals, which was correlated with immunoreactive Cx43 within stromal fibroblasts and vascular elements. No Cx26, Cx32, or Cx43 immunostaining was detected in luminal endometrial epithelium in either the mare or the pig at any stage of the estrous cycle or pregnancy. In contrast, endometrial glands of the mare exhibited a spatiotemporal pattern of Cx43 expression in the apicolateral plasma membrane which, when present, colocalized with the tight junction-associated protein, ZO-1. Uterine glandular Cx43 expression in mares was present from day 3 postovulation through day 14 of diestrus and until day 23 of pregnancy, whereas Cx43 was absent within uterine glands during seasonal anestrus, estrus, and after day 30 of pregnancy. Primary cultures of equine endometrial epithelial cells expressed both immunoreactive Cx43 and significant gap junction-mediated intercellular communication (GJIC) which was rapidly upregulated by 1.0 mM 8-bromo-cAMP or blocked with 1.0 mM octanol. No GJIC or connexin protein was detected in cultured porcine epithelial cells despite incubation with a variety of agents, including 8-bromo-cAMP, steroid hormones, retinoic acid, and/or prolactin.

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Fourteen mares were used to examine the efficacy of ultrasound for evaluation of the mare's cervix during the estrous cycle. During the physiologic breeding season, uterine and cervical characteristics were examined by palpation and ultrasound from Day 10 of the estrous cycle through Day 12 postovulation. During the observed cycle, mares were bred by artificial insemination. The cervical ultrasound exam included observations of diameter and cervical sonographic characteristics using a five-point cervical rating system. Blood was collected on Days 0, 6, and 12 postovulation and analyzed for progesterone.Cervical evaluations by palpation and by sonography were highly correlated (r = 0.86). Cervical diameter was best correlated with findings obtained via the ultrasound rating system (cervical score) (r = 0.68). A 71% pregnancy rate was achieved. Mean progesterone concentrations for Days 0, 6, and 12 were 0.24, 13.15, and 11.41 ng/ml, respectively. The mean cervical diameters on Day 12 postovulation for mares that became pregnant (BP) and mares that failed to become pregnant (NBP) were 2.85 cm and 3.43 cm, respectively. In this study, cervical echography was shown to be a useful adjunct to cervical assessment by palpation in cycling mares.

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