DESCRIPTION: Brain microvasculature is one of the multiple sites that are susceptible to lead toxicity. Unfortunately, the mechanisms underlying this toxicity are unknown. Unfortunately, the mechanisms underlying this toxicity are unknown. It is well-established that microvessel development is regulated by numerous events, including local proteolysis, cell- extracellular matrix interactions, and angiogenic factors. The primary objective of this proposal is to determine whether Pb-induced microvessel toxicity results from the toxicant's effect on specific proteolytic pathways, microvessel-matrix interactions, or angiogenic factors such as cytokines. Both in the in vivo and in the vitro models will be used to address these objectives. Aim 1 will determine whether neonatal lead exposure alters rat brain microvessels or expression of BBB proteins. Immunohistochemical, biochemical and molecular biological methods will be used to examine microvessel formation and expression of BBB proteins such as gamma glutamyl transpeptidase, glucose transporter type-1, p- glycoprotein, transferrin receptor, and endothelial barrier antigen. Aim 2 will examine if lead alters the plasminogen activator (PA) and collagenase proteolytic pathways in the rat neonatal microvessels and in the in vitro astroglial-induced microvessel formation. Biochemical methods will be used to quantify changes in the proteolytic activity and of specific proteases and protease inhibitors. Changes of expression and distribution of specific proteases and protease inhibitors will be examined using immunohistochemistry, in the situ hybridization, and Northern blotting. Aim 3 will determine whether lead alters the expression of proteins which regulate interactions with the extracellular matrix. Effects of lead on laminin, collagen, proteoglycans, SPARC, thrombospondin and angiogenic cytokines associated with neonatal brain capillaries in the vitro glia-induced microvessels, will be determined. It is anticipated that these studies will expand our understanding of normal microvessel development and how these critical events are affected by lead.