Unconjugated 125-radiolabeled peptides injected into the rats day post-MI were detectable within the heart 3 hours post-injection, but only at trace levels 24 hours post-injection. Additionally, biodistribution analysis showed that the unconjugated peptides were JANEX-1 predominantly in other organs��e.g. liver, intestines��instead of the heart. Not only did the MHC-Ab concentrate the peptides within the MI, but it also allowed the peptides to remain within the MI for Jatropholone-B longer periods of time. Hence, in order to expect any benefit from peptide treatment after acute MI, it was necessary for us to target them with an antibody. However, even though most of the antibody was targeted to the infarct region of the heart, there were still trace levels in other organs, which could result in neoplastic angiogenesis within these organs. Future studies will need to be conducted to fully assess the effect of these trace levels in other organ systems in producing angiogenesis. Our in vitro data found three peptides HepI, HepIII, RGD that exhibited similar properties, although to a lesser extent, as their source proteins, particularly in terms of promoting endothelial cell adhesion, proliferation and haptotactic migration. Nanogram amounts of either HepIII or RGD were sufficient to promote significant movement of endothelial cells. This is the same order of magnitude of peptides that we injected into our rats. Using fluorescently labeled peptides, we had determined that our conjugation resulted in crosslinking,3 moles of peptide per mole of antibody. The presence of the ECM-derived peptides could promote the migration of endothelial cells to the infarct site. Cells interact with the ECM via receptors, including integrins. Yet, these receptors only interact with certain regions of an ECM protein. Our Western blot analysis showed activation of Erk1/2 by HepI, HepIII, and RGD. Activation of the Erk1/2 signal transduction pathway in ECs is critical for EC proliferation and angiogenesis. HepIII has been shown to interact with a2b1 and a3b1 integrins, thereby promoting cell adhesion to the peptide. There is some evidence that a2, a3, and b1 integrin subunits can also interact with HepI. RGD has been shown to interact with the integrin avb3.