The objectives of the proposed research are: (1) To determine the types of prostaglandins (PGs) synthesized by the cerebral vasculature, including large arteries and veins and microvessels; (2) To characterize the effects/agents/factors that influence PG synthesis and release in these preparations; (3) To study in detail the metabolism of PGs in the cerebral circulation, specifically, the activities of 15-OH dehydrogenase, delta 13 reductase, and 9-keto reductase; and (4) to characterize the effects of PGs on cerebral microvessel functions as an in vitro blood-brain barrier model. The characterization of PG synthesizing enzymes and the endoperoxide metabolizing enzymes will be approached by a systematic study with labelled substrates (14C-arachidonic acid, 14C-PGH2); release of PGs will be assayed with specific radioimmunoassays. Metabolism will be studied by the use of labelled substrates (3H-PGI2, 14C-PGF2 alpha 14C-PGE2). The metabolizing enzymes will be carefully characterized with respect to cofactor requirements, pH, substrate variations, end-product inhibition. These studies will enable the prediction, and possibly, the relative concentrations of prostaglandins and prostaglandin metabolites released into the cerebral circulation. To investigate the effects/roles of PGs on the blood-brain barrier function of the microvasculature, the actions of various PGs and PG synthetase inhibitors on labelled amine, insulin and sucrose uptake in isolated microvessels will be determined--this approach is designed to study carrier mediated transport versus diffusion between endothelial cells.