The glomerular

filtration rate (GFR) was determined using creatinine Proteasome inhibitor clearance normalized by corporal surface area (ml/min per cm2). The concentrations of sodium and microcystins were determined in plasma and 24 h urine using commercial kits following the manufacturer’s instructions (Gold Analisa and Doles, Brazil and Beacon Analytical Systems, USA). The results obtained from plasma and urine were used to calculate the clearance of sodium and microcystin using the following equation: (Urinary Flow X Urinary Solute Concentration)/Plasma Solute Concentration = ml/min. The equation to determine the fractional excretion of microcystin (FEMCYST in %) was (Microcystin Clearance/Creatinine Clearance) × 100. Right medulla kidney samples were homogenized in ice-chilled phosphate buffered saline buffer in a 1.5-ml centrifuge tube. The homogenates were centrifuged, and the supernatants were immediately frozen in liquid nitrogen and stored at −20 °C for biochemical analyses. Total Selleck MG132 protein content in the samples was determined using the Bradford method (Bradford, 1976). Concentration of free MCYST in the renal tissue homogenates, serum, feces and urine was determined by ELISA using commercial kits (Beacon Analytical Systems, Portland, ME-USA) following the manufacturer’s instructions after sample dilution when necessary. The quantification of thiobarbituric acid reactive

substances (TBARS) was used to evaluate lipid peroxidation in the renal tissues. The method detects MDA during an acid-heating

reaction as previously described by Draper and Hadley (1990). Briefly, the samples were mixed with 1 ml of 10% trichloroacetic acid and 1 ml of 0.67% thiobarbituric acid; subsequently, the samples were heated in a boiling water bath for 30 min. TBARS were determined by absorbance at 532 nm and expressed as MDA equivalents (nM/mg protein) calculated from a standard curve produced with MDA standard dilutions. CAT activity was measured by PFKL the decrease in the rate of hydrogen peroxide added to the homogenates. This substrate concentration was determined by absorbance at 240 nm (Aebi, 1984). GST activity was measured by the formation kinetic of glutathione (GS)–dinitrobenzene (DNB) conjugate after the reaction of 1-chloro-2,4-dinitrobenzene (CDNB) with GSH. The absorbance of GS–DNB was determined at 340 nm (Habig et al., 1974). The assay was based on the reaction of GSH with 5,5-dithiobis (2-nitrobenzoic acid) (DTNB), which produces the 2-nitro-5-thiobenzoate (TNB) chromophore. The rate of formation of TNB, determined by the absorbance at 412 nm, is proportional to the concentration of GSH in the sample. To determine GSSG, the samples were treated with 2-vinylpyridine, which covalently reacts with GSH (but not GSSG). The excess 2-vinylpyridine was neutralized with triethanolamine.