Maternal plasma levels of vascular endothelial growth factor and interleukin-6 in the term-pregnant and non-pregnant rats

ABSTRACT

Female reproductive functions are associated with changes in the level of systemic cytokines which play pivotal roles during ovulation, development of corpus luteum, embryo implantation, and labor. Although many studies reported elevated level of VEGF during early pregnancy and IL-6 at the onset of labors, there is still incomplete elucidation of the level of these systemic cytokines in the very-late pregnancy or in the non-pregnant states. The purpose of this study was to determine the maternal plasma level of vascular endothelial growth factor (VEGF) and interleukin-6 (IL-6) in the term-pregnant and non-pregnant rats to see if their levels are changed at the very end of pregnancy. Blood samples were collected from twelve term-pregnant rats and compared by aged-matched seven non-pregnant rats. Plasma was separated carefully from all samples and the concentrations of VEGF and IL-6 were determined by ELISA techniques. The plasma concentration of VEGF was significantly higher in the non-pregnant rats (0.237 pg/ ml) than in the term-pregnant (0.2 pg/ ml; P < 0.001). The plasma concentration of IL-6 was significantly higher in the term-pregnant rats (50.12 pg/ ml) than in the non-pregnant ones (40.19 pg/ ml; P < 0.05). These findings suggest that the level of VEGF is decreased few days before labor possibly to decrease the ovarian blood flow and to cause luteolysis while the level of IL-6 is increased at the end of pregnancy possibly to cause a local inflammation. Together, these changes are necessary to stimulate the onset of labor.