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Urinary prostaglandin E 2 and vasopressin excretion in essential fatty acid‐deficient rats: Effect of linolenic acid supplementation
Author(s) -
Hansen Harald S.,
Jensen Benny
Publication year - 1983
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02534534
Subject(s) - endocrinology , medicine , excretion , weanling , chemistry , arachidonic acid , radioimmunoassay , urinary system , urine , vasopressin , creatinine , fatty acid , kidney , biology , biochemistry , enzyme
Three groups of weanling male rats were fed on a fat‐free diet for 13 weeks. One group received only the fat‐free diet (FF rats), the other 2 groups received the fat‐free diet and a daily supplement of 2 energy% ethyl linoleate ([n−6] rats), or 2 energy% ethyl linolenate ([n−3] rats). Urinary excretion of prostaglandin E 2 (PGE 2 ), immunoreactive arginine vasopressin (iA VP), and kallikrein were determined. PGE 2 was quantitated with a radioimmunoassay having 4.9% cross‐reactivity with prostaglandin E 3 (PGE 3 ). After 4 weeks on the diet, water consumption and urinary iAVP excretion increased significantly in the FF rats and the (n−3) rats compared with the (n−6) rats. Urinary PGE 2 excretion was the same for all 3 groups during the first 10 weeks; thereafter it decreased in FF rats and (n−3) rats compared with the (n−6) rats. There was no difference in urinary PGE 2 excretion between the FF rats and the (n−3) rats, even though large differences were found in the percentage of arachidonic acid (20∶4[n−6]), icosapentaenoic acid (20∶5[n−3]), and icosatrienoic acid (20∶3[n−9]) of total kidney fatty acids as well as of kidney phosphatidylinositol fatty acids. Fractionation of urine extracts on high performance liquid chromatography with radioimmunoassay detection indicated that (n−3) rats excreted very little PGE 3 , if any. Urine output followed the same pattern, as did urinary PGE 2 excretion. Urinary kallikrein was estimated at week 12 only. It was found to be significantly lower in FF rats and (n−3) rats. Increased water consumption and increased urinary iAVP excretion seem to be early symptoms (after 4 weeks) of EFA deficiency, whereas decreased urine output and decreased urinary PGE 2 excretion occur much later (after 10 weeks). Two energy% linolenate supplementation to a fat‐free diet did not change the appearance of any of the measured EFA‐deficiency symptoms except for a slightly improved growth rate. There was no evidence of a significant urinary PGE 3 excretion in spite of an extreme enrichment of kidney lipids with 20∶5(n−3). It is suggested that urinary PGE 2 is derived from precursors delivered from an arachidonic acid pool, which is rather resistant to restriction in dietary linoleate.