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Cyclosporine (CsA)-treated female Wistar rats, in dose of 37.5 μM (45 mg)/ kg/day for 7 days, exhibited significantly decreased creatinine clearance (Ccr), and provoked body weight loss (BWL), which is consistent with the development of nephrotoxicity (NT). Urine volume (V) did not change and proteinuria (PU) was not provoked. These changes were associated with significantly diminished ratios of urinary PGE₂/TXB₂ and 6kPGF_1α/TXB₂ excretions. Light-microscopic (LM) sections of rat kidneys showed that all kidneys were affected but the lesions (mainly diffuse vacuolization) were reversible. When CsA-treated animals were pretreated with ketanserine (KTS), which antagonizes (a) the direct vasoconstrictor effect of serotonin (5-HT), and (b) the amplifying effects of 5-HT on other vasoactive substances (such as noradrenaline (NA), α₁-receptors, histamine, H₂ receptors, and prostaglandin F_2α), Ccr and urine volume significantly increased, BWL was partially prevented and the ratios of urinary PGE₂/TXB₂ and 6kPGF_1α/TXB₂ excretions were significantly enhanced. LM sections showed that only 5 of 9 rats were affected but the lesions were of less importance. These observations indicate that the NT induced by CsA in our studies was mediated by 5-HT, a potent vasoconstrictor agent, and by the metabolites of arachidonic acid. However, other vasoactive agents and additional mechanisms could also be implicated.

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In this study we investigated the role of a mixture of n-6/n-3 essential fatty acids, in the cyclosporine model nephrotoxicity. Administration of cyclosporine in rats decreased creatinine clearance and provoked body weight loss, but it did not induce proteinuria and did not alter the urine volume. These changes were associated with decreased urinary ratios of prostaglandin E/thromboxane B and prostaglandin I/thromboxane B excretions. Light microscopic sections showed that 100% of the animals were affected by histological tubular lesions on their kidneys. Administration of cyclosporine to animals fed for 3 months on standard chow containing a mixture of n - 6/n - 3 essential fatty acids, restored creatinine clearance, augmented urine volume and prevented body weight loss. The improvement of renal function was accompanied by increased urinary ratios of prostaglandin E/thromboxane B and prostaglandin I/thromboxane B excretions. Light microscopic sections showed that only 40% of the animals demonstrated histological tubular lesions, of minor importance, to their kidneys. Our results suggest that the metabolites of arachidonic acid can play important role in the development of cyclosporine-nephrotoxicity because they increase the levels of thromboxane A and that the enchanced synthesis of prostaglandins (E) and (I) induced by a mixture of n - 6/n - 3 essential fatty acids, could play a beneficial role in the prevention of this renal dysfunction.