Abstract: Objective To explore the biological effects of the luteinizing hormone receptor （LHR） and vascular endothelial growth factor （VEGF） on the ovary of mice during periimplantation. Methods The immunohistochemistry SABC method and image analysis were used to study the distribution and changes of the LHR and VEGF in Kunming mouse(EM>n/EM>=28) ovary during estrous，pregnancy of day 1, day 4 and day 6 stage. Results The expression of LHRimmunoreactive substance and that of VEGF-immunoreactive substance had the same distribution and changes. Compared with other groups,the level of LHR-immunoreactive substance and that of VEGF-immunoreactive substance increased highly on the stroma cells around larger growing follicles in estrous group (P<0.05). Along with the pregnancy, the positive immunostaining for LHR and VEGF increased gradually on the granulosa lutein cells, and reached the highest level on day 6 of pregnancy. Positive immunostaining for LHR or VEGF on some endothelia and blood cells were observed in day 1 of pregnancy or estrous group respectively. Form day 1 of pregnancy, the theca cells had positive immunostaining for LHR. Conclusion The expression of LHR and VEGF is closely r

Key words: Luteinizing hormone receptor, Vascular endothelial growth factor, Peri-implantation, Ovary, Immunohistochemistry, Mouse