We studied the effects of fish oil on the progression of renal insufficiency in rats with subtotal nephrectomy. Five weeks after a 1-2/3 nephrectomy, sixteen rats were fed two different diets which differed only in fat composition. Lipid in the control diet was primarily beef tallow; that of the experimental diet, menhaden oil. Fish oil-fed rats had significant increases in plasma creatinines, decreases in urinary PGE2 and accelerated death rates. An additional twelve rats underwent 1-1/3 nephrectomies, and the same dietary manipulations, followed by renal clearance, histologic and biochemical studies after 12 weeks on the diets. Fish oil-fed rats again did worse, with decreased glomerular filtration rates and filtration fractions, more proteinuria and more glomerular sclerosis. Glomeruli and slices of cortex, medulla and papillae from rats fed fish oil produced much less PGE2 and TXB2 than dietary controls. Fish oil-induced suppression of renal PGE2 may be deleterious in this model and may outweigh the beneficial effect derived from TXA2 suppression. In contrast to fish oil's potentially therapeutic role in cardiovascular and immune-mediated renal disease, this diet is detrimental in rat renoprival nephropathy. This illustrates the importance of examining the effects of fatty acid manipulation individually for each disease entity.

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