1. S. Acuña 1*, C. López 1, E. Fumuso 2, M. Herrera 2, E Rodríguez 2, D. Rogan 3, C. Tasende 1 1* Veterinary faculty, Montevideo, Uruguay, 2 Faculty of Veterinary Science, Tandil, Argentina, 3 Bioniche Life Sciences Inc., Belleville, Ontario, Canada. 1* saap22@ adinet.com.uy EFFECT OF IMMUNOMODULATION ON OXYTOCIN RECEPTOR IN THE ENDOMETRIUM OF HEALTHY ENDOMETRITIS RESISTANT MARES Materials and Methods Results Acknowledgements To : P. Rubianes for technical assistance. The distribution of endometrial oxytocin receptor, in mares treated with an immunomodulator during estrous cycle has not been document. Our purpose was to investigate the distribution of endometrial oxytocin receptor in the endometrial of healthy mares resistant to endometritis treated with an immunomodulator 1.Fumuso E., et al. (2003). Vet. Immun. and Immunopat. 96: 31-41. 2.Acuña S., et al. (2008). ICAR Congress. References An immunoperoxidase staining technique was used to visualize Oxytocin Receptor (ROx) immunoreactivity in the endometrial of healthy resistant mares to endometritis, during of the estrous cycle (Fig. 1). The staining of ROx was observed in the luminal epithelium (LE), superficial glandular epithelium (SGE) and deep glandular epithelium (DGE) (Fig. 2). The average staining intensity was analyzed by ANOVA; including effect the epithelial type, stage of estrous cycle and interaction between these as the main interactions (Fig. 3). Fig. 2. Immunohistochemical localization of ROx in the endometrium of HRM. (A)= epithelial localization in biopsies (100x), (B)= negative control (400x), (C)=ROx positive sample showing LE and SGE cells (400x) and (D) ROx positive sample showing DGE (400x). At the level in the endometrium of mares susceptible to endometritis, the response to immunomodulation with MCC-V has proven to be beneficial by modulating the inflammatory response (1). Besides its effect on HRM, MCC-V has been shown to increase the presence of endometrial tissue leukocytes for 24 hours post-treatment (as happens after breeding) with no negative effects on estradiol or progesterone receptors (2). The decline in ROx during ovulation and early diestrus confirms previous findings, and demonstrates the lack of any adverse effect associated with the use of MCC-V in HRM. These data suggest that prophylactic immunomodulation with MCC-V could be safely used in HRM; particularly for embryo transfer or when breeding with expensive semen. Discussion and Conclusion Fig. 3. Staining intensity for ROx in endometrial tissue of HRM during the estrous cycle treated at oestrous with MCC-V intrauterine administration. Bars (means ± standard errors) a,b,c are significant differences between epithelial types and * E is different to 24hPT, OvPT and d6POv. P<0.05. Healthy endometritis resistant mares (HRM, n=7), received 1500µg of an immunomodulator (mycobacterial cell wall-DNA complex (MCC-V), Bioniche Life Sciences Inc., Canada), by intrauterine administration at the beginning of estrus. Fig. 1. Days that biopsies samples were taken for ROx determinations. O: Oestrous (ovarian follicles >29 mm, fold and endometrial oedema) immediately before treatment with MCC-V; 24hPT: 24 h post treatment; OvPT: around the ovulation (± 12h) and d6POv: diestrous (6 days after ovulation). The follicular dynamic was followed by ultrasonography. C A B C D LE SGE DGE LE SGE LE SGE DGE Differences in ROx expression between epithelial type (P<0.001) and stage of the estrous cycle was observed (P<0.05). The greatest intensity of staining was found in DGE, was intermediate in LE and was lowest in SGE at all stages of the estrous cycle. In all three epithelia tested, staining intensity decreased (P=0.008) from O to 24hPT, and there were no differences between 24hPT, OvPT and d6POv. (Fig. 3) a,* b,* c,* a b c a b c a b b O