DIETARY ALTERATION OF DIHOMOGAMMA-LINOLENIC ACID ARACHIDONIC-ACID RATIO IN A RAT 5 6-RENAL-ABLATION MODEL/

Interest in the modulation of renal diseases by polyunsaturated fatty acids (PUFA) led this group to examine the effects of borage oil (BO) and corn oil (CO) in the rat 5/6-renal-ablation model, BO is a rich so urce of gamma-linolenic acid (GLA; 18:3n-6), which is elongated to dih omogamma-linolenic acid (DGLA; 20:3n-6). CO is a rich source of linole ic acid (LA; 18:2n-6), a GLA and arachidonic acid (AA; 20:4n-6) precur sor, The purpose of this study was to assess whether an increased DGLA :AA ratio as provided by BO would confer benefits beyond those provide d by LA present in corn oil, Forty rats were used for the experiment. Seven rats were used for presurgery measurements. The remaining animal s were subjected to 5/6 nephrectomy. Surviving rats (N = 30) were fed regular laboratory diet (RLD) for 7 days, at which time seven rats Wer e used to obtain 1-wk postnephrectomy data. The remainder were then al located to receive either RLD (N = 8), 15% BO (N = 8), or 15% CO (N = 7) diets for 20 wk. Body weight, renal phospholipid levels, renal func tion (proteinuria and GFR), glomerular histology, glomerular macrophag e infiltration, urinary prostaglandin levels (thromboxane B-2 (TxB(2)) , 6-keto-PGF(1 alpha)), plasma lipid levels, and blood pressure were m easured. Diets were well tolerated by all groups with a similar age-re lated gain in weight throughout the study. Efficacy of the PUFA diets was confirmed by alteration in renal tissue phospholipids; LA decrease d in the RLD and BO groups, but not in the CO group. AA was higher in the BO and CO rats, but only the BO group showed a rise in GLA and DGL A incorporation. Proteinuria increased progressively in the RLD group but remained at 1-wk postsurgery levels in the BO and CO groups. Decli ne in GFR and mesangial expansion were significantly lessened by BO su pplementation only, Both PUFA diets limited glomerulosclerosis and mac rophage infiltration, but direct comparisons between BO and CO groups revealed significantly less glomerulosclerosis and macrophage infiltra tion in the BO group. Both BO and CO attenuated the rise in the TxB(2) excretion rate and restored the 6-keto-PGF(1 alpha):TxB(2) ratio to t he 1-wk postsurgery level. Plasma lipid levels rose in all groups, but the rise in cholesterol level was less in the BO and CO rats, CO bein g the most efficacious in this regard, BP increased progressively in R LD rats, but not in the BO and CO groups, BO providing a markedly grea ter hypotensive effect. In summary, both CO and BO supplemented PUFA d iets limited glomerular injury in the renal-ablated rats. However, BO supplementation was more effective than CO supplementation at preservi ng GFR, limiting mesangial expansion and glomerulosclerosis, and reduc ing glomerular macrophage infiltration.