Vascular endothelial growth factor receptor-1 (VEGF R1), also known as Flt-1, is a receptor tyrosine kinase (RTK) specific for the angiogenic factors VEGF (VEGF-A), PlGF, and VEGF-B. There are two forms: membrane-bound (mbVEGFR) and soluble (sVEGFR), depending on alternative splicing.
Experimental and clinical administrations of sVEGF R1 have been employed successfully in the prevention of neovasculogenesis and tumor growth. The serum/plasma level of sVEGF R1 may vary by pathology, and may have prognostic value. It has been suggested that sVEGF R1 levels should be presented alongside VEGF levels in experimental and pathological conditions. High levels of sVEGF R1 reportedly occur in the plasma during pregnancy and in patients with essential hypertension. Significantly lower levels have been observed in the plasma of patients with cardiovascular disease and in smokers.