Platelet Derived Endothelial Cell Growth Factor (PD-ECGF) is a protein that supports the growth and repair of blood vessels. However, as it is a scientific term, there are no direct antonyms for it in common parlance. However, if we break it down into its constituent words; Platelet, Derived, Endothelial, Cell, Growth, and Factor, we can find antonyms for each on their individual level. For instance, the antonym of "platelet" would be "clotting inhibitor," "Derived" would be "original," "Endothelial" would be "nonvascular," "Cell" would be "organism," "Growth" would be "reduction," and finally, "Factor" would be "noncontributing.