Changes in bradykinin and bradykinin B2-receptor during estrous cycle of mouse

The aim of the study was to investigate changes in the abundance of bradykinin and bradykinin B2-receptor in the ovary of mice during its estrous cycle. Changes in the abundance of bradykinin were correlated with changes in bradykinin B2-receptor in order to determine the functional significance of this peptide for follicular development, ovulation and luteinization. Bradykinin immunoreactivity was mainly observed in the granulosa cells of antral follicles, especially around the oocytes and lining the antral cavity during proestrus and estrus phases of the cycle. Recently formed corpora lutea showed mild immunoreactivity for both bradykinin and bradykinin B2-receptor. During diestrus 1 and diestrus 2, bradykinin and bradykinin B2-receptor immunostaining was mainly found in the corpora lutea and mildly in the antral follicles. Immunoblot analysis for bradykinin and bradykinin B2-receptor attained a peak during late evening in proestrus, which may be the time of the LH surge. Thereafter bradykinin and bradykinin B2-receptor declined sharply during the estrus phase. When the concentration of bradykinin was correlated with bradykinin B2-receptor throughout the estrous cycle, they showed strong positive correlation. Thus, this study indicates that the levels of bradykinin and bradykinin B2-receptor both simultaneously regulate estrous cycle and are important components for the reproductive process.