ABSTRACT
BACKGROUND: Vascular endothelial growth factor (VEGF) is the most potent stimulator of angiogenesis. It mediates its activity through two membrane-bound receptors, VEGFR-1 and VEGFR-2, both expressed in the placenta. Beginning in early pregnancy, the soluble form of the first, sVEGFR-1, binds and inhibits most of the biological actions of circulating VEGF. After delivery, it disappears from the maternal circulation. METHODS: We determined the biological elimination rate of endogenous sVEGFR-1 after term pregnancy in serial venous samples obtained during and after elective Caesarean sections (n=8), and we demonstrated the relationship between serum sVEGFR-1 and VEGF after mid-trimester legal termination of pregnancy (n = 5), by analysing their concentrations using immunoassays (ELISA). RESULTS: The disappearance of sVEGFR-1 from circulation after Caesarean delivery was biphasic with a rapid half-life of 3.4 h (2.2-7.5 h; median, range) and a slow one of 29 h (17-94 h). After mid-trimester legal termination of pregnancy the sVEGFR-1 concentrations decreased and those of free VEGF simultaneously increased with a highly significant negative correlation with each other (r = -0.90, P < 0.0001). CONCLUSIONS: The disappearance of endogenous sVEGFR-1 after pregnancy is biphasic, and it is associated with a simultaneous increase in free VEGF concentrations.