Soluble fms-like tyrosine kinase-1 （sFlt-1 or sVEGFR-1） is a tyrosine kinase protein with antiangiogenic properties. A non-membrane associated splice variant of VEGF receptor 1 （Flt-1）, sFlt-1 binds the angiogenic factors VEGF （vascular endothelial growth factor） and PlGF （placental growth factor）, reducing blood vessel growth through reduction of free VEGF and PlGF concentrations. In humans, sFlt-1 is important in the regulation of blood vessel formation in diverse tissues, including the kidneys, cornea, and uterus. Abnormally high levels of sFlt-1 have been implicated in the pathogenesis of preeclampsia.

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