Enzyme-linked immunosorbent assay (ELISA)
The concentrations of fms-like tyrosine kinase 1 (sFlt1) and placental growth factor (PlGF) were determined with specific ELISA kit from Westang Biotech Co Ltd (Shanghai, China). A commercial ELISA kit from Cayman Chemical (catalogue #: 501320) was used to measure the corticosterone levels in rat serum and placental tissues according to the manufacturer’s instruction.