Fish oil diet decreases prostacyclin and increases resistance in isolated rat kidneys

The mechanisms whereby diet-induced alterations in fatty acids may affect renal structure and function are unknown. Kidneys from rats fed chow supplemented with 18% (wt/wt) coconut oil (CO, n = 8), sunflower seed oil (SO, n = 7), or fish oil (FO, n = 8) were isolated from systemic influences of the diets and perfused with a cell-free medium. The FO diet caused a twofold reduction in prostaglandin (PG) I₂ (urine excretion of 6-keto-PGF(1α) compared with SO and CO. Urine PGE₂ and thromboxane (Tx) B₂ were similar in the three diet groups. There was a 22% reduction in perfusate flow associated with decrease in PGI₂ in the FO group (42 ± 6 ml·min^-1·g^-1) compared with the CO (54 ± 7 ml·min^-1·g^-1) and SO (54 ± 8 ml·min^-1·g^-1) groups (mean ± SD, P < 0.05). The glomerular filtration rate (GFR) was similar in the three groups during the initial base-line determination but subsequently declined to a greater degree in the FO group. Morphologically, tubular injury was most extensive in the FO group, and the distribution of the injury indicated that it was caused, at least in part, by ischemia. The decline in GFR and the degree of histological injury were most closely linked to the diminished PGI₂ production. Thus dietary FO supplementation caused decreased renal PGI₂, increased renal vascular resistance, and an increased susceptibility to ischemic tubular cell injury in the isolated kidney.