Abstract
Alpha-1-acid glycoprotein (AGP) is one of the major acute phase proteins responded to inflammation. AGP is mainly synthesized in the liver, but other organs like spleen, lung, kidney, uterus, ovary, and placenta have been shown to express AGP mRNA with much lesser extent. The biological function of AGP remains still unknown, however, various activities relating to immunomodulating properties have been described. We aimed to investigate the AGP mRNA expression (real-time PCR) in the bovine corpus luteum (CL) at different reproductive stages. The results exhibit that 1) AGP mRNA expression is higher in mid CL (P<0.05) compared with early, late and regressing CL, 2) CL from Day 29-33 of pregnancy expresses AGP mRNA higher (P<0.001) than cyclic mid CL, 3) luteal cells express AGP mRNA higher than luteal endothelial cells, and 4) neither PG-induced luteolysis nor LPS-induced CL suppression resulted in changes in AGP mRNA expression in CL. The results indicate that the high mRNA expression of AGP in the CL coincides with high P4 synthesis in the CL under physiological conditions. In addition, a large number of PMNs observed in early and regressing CL, but none in mid CL, suggesting a known AGP activity to bind E-selectin on endothelial cells thereby possibly blocking PMNs to infiltrate to the mid CL. On the other hand, a suppression of P4 synthesis and a stimulation of inflammation by PG-induced regression or LPS-injection did not change AGP mRNA expression. Collectively, bovine CL expresses AGP mRNA and its changing profiles positively relate to P4 synthesis in CL of cycle and pregnancy, but not to inflammation. Thus, a local AGP system in CL may play a physiological role to support CL function.
