A fish oil diet preserves renal function in nephrotoxic serum nephritis

Fish oil diets preserve renal function in murine lupus, but we have found that these diets accelerate renal deterioration in renoprival nephropathy. In this study we examined the effects of dietary fish oil in accelerated nephrotoxic serum nephritis. For 1 month, 14 female rats were fed diets that differed only in fat composition, containing either menhaden (fish) oil or beef tallow (control). Rats were then preimmunized with rabbit IgG and, 5 days later, were injected with nephrotoxic serum. Glomerular filtration rate (GFR) was measured continuously in conscious animals by means of intraperitoneal 14C-labeled inulin minipumps. Fish oil-containing diets markedly attenuated the nephrotoxic serum-induced decline in GFR and the rise in proteinuria and significantly reduced glomerular prostaglandin E2 and thromboxane A2. The results of tests of renal histology showed no differences between the two groups. Five days after preimmunization, rats fed fish oil had more rabbit IgG remaining in their serum and had mounted less of an antibody response to the rabbit IgG. Fish oil diets also resulted in an attenuated disappearance of injected 14C-labeled rabbit IgG. In vitro, peritoneal macrophages from rats fed fish oil took up less rabbit IgG than macrophages from rats fed control diets. Thus the beneficial effects of a fish oil diet may result from defective immune surveillance and from alterations in eicosanoids.