CHARACTERIZATION OF RENAL NONCYCLOOXYGENASE ARACHIDONATE METABOLISM

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Renal cytochrome P-450 catalyzes the oxidative metabolism of arachidonic acid to epoxyeicosatrienoic acids (EETs), omega and omega-1 alcohols (19- and 20-OH-AA). These metabolites are unique to this enzyme system and display several potent biological activities, including stereoselective renal vasoconstriction, reduction in the glomerular filtration rate, alterations in the permeability of renal epithelia to sodium and potassium and, modulation of the hydroosmotic responses to vasopressin. The significance of this branch of the arachidonate cascade to renal function has been highlighted by a) the demonstration of endogenous, enantioselective, formation of EETs, b) the regulation of the enzymes involved and/or their metabolites by experimental hypertension, dietary salt loading of deoxycorticosteroid acetate (DOCA) treatment and, c) the preferential expression of the cytochrome P-450 4A2 gene in hypertensive (SHR) rats. More recently, the demonstration of EET as endogenous constituents of human kidney and their increased urinary excretion during pregnancy induced hypertension suggest that renal cytochrome P-450 may fulfill yet unidentified roles in kidney physiology and/or pathophysiology. As part of a multidisciplinary and comprehensive approach to delineate the significance of this metabolic pathway to kidney function, this project proposes to utilize standard methods of protein purification, enzymology, immunochemistry, chromatography and GC/MS to: 1) continue the molecular, biochemical and chemical characterization of the renal cytochrome P-450 arachidonate monooxygenase isoforms and of their metabolites, 2) analyze functional/biochemical correlations after the experimental manipulation of renal physiology by functionally relevant protocols of animal treatment, 3) investigate the effects of these manipulations in the regulation of the enzymes and/or the metabolites of this branch of the arachidonate cascade, and 4) utilize animal models of experimental hypertension to define potential relationships between the biochemistry of cytochrome P-450 arachidonate metabolism and genetically controlled alterations in kidney physiology and pathophysiology. It is proposed that this branch of the arachidonic acid cascade is an integral part of the adaptive response of the kidneys to a dietary salt overload and, therefore may be involved in the pathophysiology of hypertension.