Arachidonic acid metabolites, including prostaglandins, thromboxanes and products arising from alternative pathways, particularly cytochrome P450-dependent transformations, will be studied in a wide range of experimental preparations. In the rat isolated kidney, perfused by a closed-circuit system, kallikrein- and renin-releasing mechanisms will be studied during high and low perfusion pressures as well as filtering and non-filtering states, because the participation of eicosanoids in these releasing mechanisms appears to be highly selective. For example, a product of cyclo-oxygenase, possibly PGF2Alpha, mediates kallikrein excretion into the urinary compartment under conditions of high perfusion pressure only. Of particular interest is the possible participation of arachidonic acid epoxides and their metabolites which arise from the cytochrome P450-dependent pathway. These products have been shown to inhibit Na+K+ATPase and to relax vascular tissues and may also act as secretagogues intrarenally, a possibility that will be examined. Their increased formation in kidney, blood vessels and leukocytes may be induced by glucocorticoids, streptozotocin and some vasoactive peptides, such as ADH and kinins. Identification of arachidonic acid metabolites in these tissues will be based on thin-layer chromatography, high-performance liquid chromatography, and ultimately GC-MS. Streptozotocin-induced diabetes in unanesthetized rats will be studied in terms of cytochrome P450-related abnormalities of TxA2 and prostacyclin formation. Having shown a highly-active cytochrome P450 mixed function oxidase in the porcine aortic intima, arachidonic acid metabolites of the endothelium will be characterized in terms of their biological activity and identified by their chromatographic properties and mass spectra. Finally, we will attempt to determine if PGI2 acts as a renin secretagogue directly or through transformation to 6-keto-PGE1. Similar studies will be performed on coronary arteries in an attempt to determine the possible role of 9-OH prostaglandin dehydrogenase in vascular tissues.
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