Adrenomedullin and oviduct function in human and rats

Abstract

The oviduct is the part of the female reproductive tract thatserves the important function to provide a favorable environmentfor sperm maturation, fertilization, and embryo transport. Ourrecent data showed a high level of adrenomedullin (ADM) in theoviduct but the function of this hormone in the oviduct wasnot clear. The aim of our study was to measure the oviductalADM levels in relation to the ovarian cycle and the effect ofADM on the ciliary beat frequency in the rat and human oviduct.Materials and Methods: To study the effect of ADM on the oviduct,4-week-old Sprague-Dawley rats at preovulatory or post-ovulatorystages were killed and the oviducts were slit open longitudinally.The oviducts were incubated for two hours with ADM at 0, 10,100 nM or 100 nM + 1µM human calcitonin-gene-regulatedpeptide receptor antagonist, CGRP8-37. The ciliary beat frequency(CBF) was measured using a photometric method at x100 magnificationat 5 randomly selected fields per tissue strip and expressedin Hz. Human oviducts were collected from women undergoing hysterectomyfor benign disease conditions. Oviductal tissue was treatedwith ADM and/ADM with CGRP8-37 for 2 h and CBF was measuredas described above. To study the effect of sperm on the oviduct,mature epididymal sperm from adult SD rat was collected, washedand incubated in DMEM/F12 for 5 minutes. Motile sperm in themedium was collected, washed and incubated for 5 h for capacitation. 10-week old female rats were monitored for at least two regularestrous cycles. They were killed at proestrus; oviducts wereremoved and slit open and cultured with/without an insert containingcapacitated sperm (2x105) for 24 h. After incubation, a stripof oviduct tissue was taken to measure CBF and the rest of thetissue was extracted to measure ADM peptide by an EIA kit andtotal protein. Results: Our results showed that CBF was higherin the rat oviduct compared with that in human. In both cases,the CBF increased significantly with increasing concentrationof ADM (0, 10, 100 nM) and the increase was greater in the preovulatoryrat oviducts than at postovulatory ones. Both increases wereblocked by ADM receptor antagonist. Spermatozoa coincubationsignificantly enhanced the CBF and ADM production of the oviduct,but the stimulatory effect on ADM production mainly dependedon direct physical contact between the spermatozoa and the oviductalcells. Conclusion: We demonstrated that ADM played a role inthe oviduct function in human and rats. The ciliary beat inthe oviduct was stimulated by ADM produced by the oviductalepithelium. The presence of the sperm up-regulated the ciliarybeat frequency in the oviduct which may affect ova/embryo transportin this part of the reproductive tract. Part of this increasewas due to the increase in ADM secretion produced by the oviductalepithelium as a result of direct contact with the sperm. Thisaction of ADM was mediated by CGRP receptors. Acknowledgement:This work was substantially support by a grant from the ResearchGrants Council of the Hong Kong Special Administrative Region,China (HKU7736/07M).