The central hypothesis to be tested is that dietary copper, through changes in CuSOD activity, will influence tissue PG production by altering the concentration of lipid hydroperoxide activators of PGH synthetase. In addition, inter-relationships of dietary copper, PUFA, Se, and vitamin E on these processes will be examined in view of their role in radical mediated lipid hydroperoxide production and metabolism. The preliminary data support this hypothesis.
The specific aims of the proposed research are 1) to calibrate and validate measurements of lipid hydroperoxide activators of PGH synthetase using a purified, in vitro, PGH synthetase assay measured with an oxygen electrode, and also to measure these lipid hydroperoxides by a newly developed assay which specifically measures GSSG produced from these lipid hydroperoxides in the presence of SeGSP and GSH, and 2) to determine the influence of dietary copper on TXA2 and PGI2 synthesis and lipid hydroperoxide activator production in relation to tissue CuSOD and SeGSP activity. Since increased dietary PUFA may enhance lipid hydroperoxide production, and protection may be afforded in the cytosol by dietary selenium, and in membrane lipid by vitamin E, copper interrelations with 3) dietary PUFA, 4) dietary selenium, and 5) dietary vitamin E will be examined. In order to examine these processes, platelet TXA2 and aortic PGI2 production will be determined by RIA of their spontaneous degradation products. Platelet and aorta lipid hydroperoxides will be measured by both assays mentioned above, and by the thiobarbituric acid colorimetric procedure. Interpretations of lipid hydroperoxide activator and PG production will be based on assays of tissue CuSOD and SeGSP activity. For experiments on copper and PUFA interrelationships, aorta and platelet phospholipid fatty acids will be determined by HPLC separation and GC analysis to distinguish between precursor pool changes and lipid hydroperoxide effects on PG production. The long-term goal of this project are to investigate the role of nutrients in the control of oxygen radical metabolism and their influence on tissue eicosanoid synthesis. The proposed studies will provide information on the control by dietary copper of the cardiovascular significant PGs, TXA2 and PGI2. Recent analyses have shown many common U.S. diets to be low in copper.
