Glutathione peroxidase isoenzymes in human tumor cell lines.

A set of human tumor cell lines was characterized in terms of the GPx isoenzymes GPx1, -2, -3 and -4. Semiquantitative PCR was used to investigate the GPx mRNA transcripts and the GPx activity was determined photometrically. As a result of culturing under standard conditions, diverse distribution of GPx mRNA and basic GPx activity was found in the investigated cell lines. PCR results showed nearly ubiquitous existence of the isoenzymes GPx1 and GPx4. GPx2 mRNA transcript was only detected in the colonic cell line CaCo-2. After detection of the GPx3 mRNA transcripts in most of the tested cell lines, an ELISA was performed to investigate if the GPx3 protein is present as well. However, the GPx3 protein could not be detected. Glutathione peroxidases contain the amino acid selenocysteine in their active centre. Selenocysteine contains selenium instead of sulfur in cysteine. Therefore, the influence of selenium on GPx activity and GPx isoenzyme distribution was investigated. Cell culturing with additional selenium showed a clear elevation of GPx activity in Mono Mac 6 cells but no gain of mRNA transcripts or any change in the isoenzyme's distribution.

Coordinately increased lysozymuria and lysosomal enzymuria induced by maleic acid.

During the acute renal tubular dysfunction of Fanconi syndrome and type 2 renal tubular acidosis (FS/RTA2) induced by maleic acid in the unanesthetized dog, we observed: 30 minutes after the onset of FS/RTA2, the urinary excretion of lysosomal enzymes, N-acetyl-beta-glucosaminidase (NAG), beta-glucuronidase (beta-gluc) and beta-galactosidase (beta-galac), increased simultaneously with the anticipated increase in renal clearance of lysozyme; the severities of all these hyperenzymurias increased rapidly, progressively, and in parallel, all reaching a peak some 60 to 80 minutes after their onset; thereafter, while the FS/RTA2 continued undiminished in severity, the severity of the hyperenzymurias decreased rapidly, greatly, progressively, and in parallel; and sodium phosphate loading strikingly attenuated the FS/RTA2 and the hyperenzymurias. Thus, the maleic acid-induced FS/RTA2 is attended by an acute reversible-complex derangement in the renal tubular processing of proteins that: affects not only lysozyme which is normally filtered, but also NAG and other lysosomal enzymes, which are not; and is to some extent functionally separable from that of FS/RTA2. The findings suggest that the derangements in renal processing of lysozyme and lysosomal enzymes are linked, and that a phosphate-dependent metabolic abnormality in the proximal tubule can participate in the pathogenesis of both these derangements and the FS/RTA2.

Phosphate loading attenuates renal tubular dysfunction induced by maleic acid in the dog.

The metabolic pathogenesis of the complex renal tubular dysfunction of type II renal tubular acidosis and Fanconi's syndrome (RTA II/FS) acutely induced by maleic acid could depend on the occurrence of a positive feedback loop in cells of the proximal renal tubule: impaired mitochondrial oxidation----increased glucose uptake----increased formation and concentration of phosphorylated glycolytic intermediates----limitation on availability of cellular inorganic phosphate----more severely impaired mitochondrial oxidative metabolism. To test this hypothesis we intravenously administered maleic acid both alone and after initiating intravenously administered neutral sodium phosphate, sodium sulfate, or sodium chloride to 10 unanesthetized trained female dogs undergoing water diuresis. We made the following observations: 1) Administration of maleic acid alone predictably induced dose-dependent increments in urine flow (V) and in renal clearance of HCO3-, Na+, K+, and alpha-aminonitrogen and a pronounced increase in the renal clearance and excretion of citrate. 2) Prior phosphate loading, which increased the plasma concentration of phosphate from 2.5 +/- 0.20 to 11.3 +/- 2 mg/dl: a) attenuated the increment in renal clearance of HCO3- by one-half even though the filtered load of bicarbonate was higher by 37%, owing to the higher values of both GFR and plasma bicarbonate concentration that obtained with phosphate loading; b) prevented the increment in renal clearance and excretion of alpha-aminonitrogen; c) significantly attenuated the increments in V and renal clearance of K+; but d) did not affect the increment in renal clearance and excretion of citrate.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma volume expansion is necessary for edema formation in the rate with Heymann nephritis.

Edema formation in nephrotic syndrome has been attributed to intravascular volume depletion resulting from leakage of plasma water into the interstitial space and activating secondary renal sodium retention. However, clinical studies indicate that edematous patients with nephrotic syndrome may have normal or expanded plasma volumes. We evaluated the relationship between plasma volume and edema formation in control rats and rats with chronic renal failure (CRF) produced by 7/8 nephrectomy. In each group, plasma volume and 22Na space were measured during the control period and after induction of hypoalbuminemia from passive Heymann nephritis. Rats with CRF had expanded plasma volume during the initial period (4.23 +/- 0.46 vs. 3.32 +/- 0.68 ml/100 g body wt) that became significantly more expanded (to 5.44 +/- 1.16 ml/100 g body wt) when they became nephrotic as 22Na space also increased. Plasma volume and 22Na space did not change in the sham-operated rats when nephrosis was produced. Plasma renin activity was lower in the CRF rats during the control period than in the sham-operated rats and fell significantly during the nephrotic period when edema developed. Nonnephrotic rats had a plasma colloid osmotic pressure (COP) of 17.8 +/- 4.3 mmHg compared with 8.5 +/- 2.9 mmHg when nephrotic. Despite this large difference in COP, both nephrotic and nonnephrotic rats exhibited the same relationship between plasma volume and extravascular sodium space, a measure of edema formation. Hypoproteinemia is not sufficient for edema formation in the rat with passive Heymann nephritis; concomitant plasma volume expansion resulting from CRF is a necessary additional component.