Localization of granulocyte-macrophage colony-stimulating factor in the bovine reproductive tract

Granulocyte-macrophage colony-stimulating factor (GM-CSF) can increase embryo development to the blastocyst stage in cattle. The objective of the present study was to determine whether GM-CSF is present in the reproductive tract. Using Western blotting, immunoreactive GM-CSF was detected in uterine flushings from cows at days 0, 7, and 14 of the estrous cycle and from cows at days 14-17 of pregnancy. Also, GM-CSF was localized immunohistochemically to endometrium and oviduct. Patterns of immunohistochemical localization and intensity of reaction product were similar for all days of the estrous cycle. While present in several cell types, immunoreactive product in the endometrium was greatest in epithelium (especially luminal epithelium). Immunoreactive GM-CSF was also localized to epithelium in ampullary and isthmic regions of the oviduct, with intensity greater in ampulla. Staining was observed for both ciliated and non-ciliated cells. In conclusion, the bovine oviduct and endometrium contain immunoreactive GM-CSF and this molecule is present in uterine secretions. Thus, this cytokine is a potentially important intracellular regulator of endometrial, oviductal and embryonic function during early pregnancy in the cow.