Ultrastructural distribution of 36-kD microfibril-associated glycoprotein (MAGP-36) in human and bovine tissues

We observed the ultrastructural distribution of MAGP-36 by immunoelectron m icroscopy in human and bovine tissues. MAGP-36 was present in microfibrils associated with tropoelastin in skin, aorta, and spleen. It was not detecte d in microfibrils from the ocular zonule and kidney mesangium that were not associated with tropoelastin. In skin, MAGP-36 was present in both early i mmature elastic fibers and mature elastic fibers. In mature elastic fibers, MAGP-36 was localized around amorphous elastic cores at the elastin-microf ibril interface and in electron-dense bundles. Localization of MAGP-36 in e lastic fibers coincided with the distribution of lysyl oxidase, an enzyme t hat plays a pivotal role in the deposition of tropoelastin. These findings suggest that MAGP-36 may be involved in elastogenesis.