Vascular endothelial growth factor (abbreviated vegf and pronounced “veg-f”) is a peptide signaling molecule related to platelet-derived growth factor. vegf is important in the formation of the circulatory system because its signaling pathway causes the formation of blood vessels in developing embryos during normal development. tumors also produce and secrete vegf, causing the formation of new blood vessels that supply these tumors. given what you know about the different kinds of cell signaling and vegf, which one of the following statements is true?
a. vegf is an endocrine-signaling molecule because it circulates through the bloodstream inside of platelets.
b. vegf is an endocrine-signaling molecule because it is released from platelets into the bloodstream and is carried throughout the body, causing widespread activation of platelet-derived growth factor receptors on cells in a variety of tissues.
c. vegf is a paracrine signaling molecule because it binds to receptors on cells at the site where new blood vessels are needed.