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PubMed1969

Delineation of cystine and cysteine transport systems in rat kidney cortex by developmental patterns.

The impaired ability of neonatal rat kidney cortex slices to take up L-cystine at a time when the ability to accumulate cysteine is similar to that of adult tissues indicates the separate nature of the transport processes for these amino acids. Dissimilarities in dependence on oxygen and temperature are also indicative of different transport systems. The intracellular form of the amino acid was largely cysteine when either cystine or cysteine was the transported substrate although significant amounts of both were incorporated into reduced glutathione. No difference in intracellular forms was found between neonatal and adult tissue.

Aging↗
PubMed1978

24Na+-efflux from kidney cortex slices under the effect of indomethacin.

24Na+-efflux from kidney cortex slices previously saturated with 24Na+ in vivo was studied in vitro under control conditions and in the presence of 4 micrograms per ml of indomethacin. The radioactivity washout curves obtained in the effluent from cortex slices superfused with Krebs-Ringer medium at 37 degrees C indicated that Na was localized in three compartments in the cortex. Indomethacin did not influence 24Na+-efflux from the compartment that exhibited the fastest efflux; this compartment is thought to be extracellular. Indomethacin potently increased 24Na+-efflux from Na+-compartments localized intracellularly and showing a lower efflux rate (lambda 2 control = 0.156 +/- 0.042, lambda 2 indomethacin = 0.21 +/- 0.064, p less than 0.05; lambda 3 control = 0.031 +/- 0.013 lambda 3 indomethacin = 0.063 +/- 0.020 min-1, p less than 0.001). Since on the basis of earlier findings the direct effect of indomethacin on the enzymes of the active transport system can be ruled out, the present results suggest that indomethacin increases the permeability of cell membranes.

Animals↗
PubMed1993

Na+,K(+)-ATPase activity of rabbit kidney cortex membranes in ischemia and reperfusion.

The activity of Na+,K(+)-ATPase in the microsomal fraction of rabbit kidney cortex was strongly decreased by ischemia and increased slightly, but not significantly, after reperfusion. These changes were correlated with a dramatic increase in lipid peroxidation in microsomes isolated from both ischemic and reperfused kidneys. This correlation may point to irreversible impairment of the enzymatic function under the influence of either oxygen free radicals or lipid peroxidation.

Animals↗
PubMed1991

Recovery of impaired gluconeogenesis in kidney-cortex tubules of gentamicin-treated rabbits.

Rabbits were given gentamicin over a period of 10 days. At 1, 3, 5 and 10 days renal proximal tubules were isolated and glucose synthesis from several substrates was measured. A relationship between the inhibition of renal gluconeogenesis, accompanied by a decline of both pyruvate carboxylase and phosphoenopyruvate carboxykinase (PEPCK) activities, and an increased gentamicin level in kidney-cortex was noticed after 5 days of therapy. Both the rates of glucose formation from various substrates as well as pyruvate carboxylase and the cytosolic PEPCK activity recovered fully within 3 weeks after cessation of antibiotic treatment while an increase of activity of the mitochondrial PEPCK occurred during chronic administration of the drug for 10 days. It is concluded, that gentamicin-induced inhibition of gluconeogenesis is one of the events occurring during complex action of this drug on renal cortex.

Animals↗
PubMed1994

Identification of metabolic pathways of the lipid peroxidation product 4-hydroxynonenal by mitochondria isolated from rat kidney cortex.

The cytosolic lipid peroxidation product 4-hydroxynonenal (HNE) is rapidly metabolized in mitochondria isolated from rat kidney cortex. About 80% of HNE was degraded within 3 min of incubation. Main products of HNE which were identified in mitochondria were the hydroxynonenoic acid, the 1,4-dihydroxynonene and the glutathione-HNE-conjugate. Furthermore, formation of metabolites of the tricarboxylic acid cycle from HNE is suggested. The quantitative share of HNE binding to proteins was high with about 8% of total HNE consumption after 3 min of incubation. Therefore, rapid degradation of HNE by mitochondria might be involved in an intracellular antioxidative defense system.

Aldehydes↗
PubMed1978

Phlorizin stimulation of p-aminohippurate uptake in rat kidney cortex slices.

Phlorizin, 0.5 mM, increases the uptake of tritiated p-aminohippuric acid (PAH) in rat kidney cortex slices in vitro. Phlorizin also diminishes the rate of 3H-PAH washout from preloaded slices into PAH-free medium. At higher concentrations, phlorizin (5.0 mM) reduces slice uptake of 3H-PAH following short incubations but increases 3H-PAH accumulation after more prolonged incubations. Section freeze-dry autoradiography demonstrates that phlorizin inhibits secretion of 3H-PAH from cell to lumen in proximal tubules. Consequently, the increased 3H-PAH uptake and delayed washout induced by phlorizin may be attributed to effects at the antiluminal cell membrane. Phlorizin stimulation of PAH uptake occurs despite inhibition of secretion across the luminal membrane. Intracellular accumulation of 3H-phlorizin, demonstrable by autoradiography, provides direct evidence that cellular accumulation affords the glycoside access to both the luminal and antiluminal membrane in proximal tubules. These interactions between phlorizin and PAH suggest shared features of the membrane transport systems for secretion and reabsorption of sugars and organic acids in kidney.

Aminohippuric Acids↗
PubMed1989

Purification and properties of a distinct protamine kinase from the cytosol of bovine kidney cortex.

A protamine kinase has been purified to apparent homogeneity from extracts of the cytosol of bovine kidney cortex. This protamine kinase exhibited an apparent Mr = 43,000 as estimated by gel permeation chromatography on Sephacryl S-200 and an apparent Mr = 45,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified protamine kinase exhibited about 5% activity with casein, 8% with histone H2B, and less than 0.1% with histone H1, histone H4, glycogen synthase a from rabbit skeletal muscle, ovalbumin, bovine serum albumin, and phosvitin. The activity of the highly purified protamine kinase was unaffected by cyclic AMP (up to 0.1 mM), cyclic GMP (up to 0.1 mM), the heat-stable protein inhibitor of cyclic AMP-dependent protein kinase (up to 100 micrograms/ml), heparin (up to 100 micrograms/ml), EGTA (up to 1 mM), Ca2+ (up to 1 mM), calmodulin (up to 0.5 microM) in the absence or presence of Ca2+ (0.05 mM), and phosphatidylserine (up to 40 micrograms/ml) and/or diolein (up to 1 microgram/ml) in the absence or presence of Ca2+ (up to 0.5 mM). Experiments in which extracts of kidney cytosol were incubated with [gamma-32P]ATP and MgCl2 revealed that the phosphorylation of numerous polypeptides was markedly increased in the presence of the purified protamine kinase. The results indicate that this protamine kinase of kidney cytosol is a novel protein kinase.

Animals↗
PubMed1994

Citrate inhibition of rat-kidney cortex phosphofructokinase.

The regulatory properties of citrate on the activity of phosphofructokinase (PFK) purified from rat-kidney cortex has been studied. Citrate produces increases in the K0.5 for Fru-6-P and in the Hill coefficient as well as a decrease in the Vmax of the reaction without affecting the kinetic parameters for ATP as substrate. ATP potentiates synergistically the effects of citrate as an inhibitor of the enzyme. Fru-2,6-P2 and AMP at concentrations equal to Ka were not able to completely prevent citrate inhibition of the enzyme. Physiological concentrations of ATP and citrate produce a strong inhibition of renal PFK suggesting that may participate in the control of glycolysis in vivo.

Adenosine Triphosphate↗
PubMed1982

Active and inactive renin release from rabbit kidney cortex slices: effect of sodium concentration and of furosemide.

1. Active and inactive renin release by rabbit kidney cortex slices was investigated. Inactive renin was estimated as the increase in renin activity after acidification (pH 2 . 8) of slice supernatant solutions. 2. Active renin release was increased when incubation medium [Na+] was reduced. This relationship was linear (r2 = 0 . 96) over the range [Na+] = 23-133 mM. 3. For the same range of [Na+] inactive renin secretion decreased when medium [Na+] was reduced (r2 = 0 . 92). Therefore, the proportion of total renin which was in the inactive form decreased linearly as [Na+] was reduced (r2 = 0 . 97). 4. Chloride ions did not appear to be important in altering the secretion of either active or inactive renin. 5. Adding furosemide to the incubation medium in concentrations up to 40 micrograms/ml. did not change secretion of either form of renin. The action of furosemide on secretion of active and inactive renin in vivo is therefore secondary to altered renal function. 6. Regulation of the relative amount of active and inactive renin in plasma could be entirely an intrarenal event. It is not essential to invoke a plasma activating enzyme for inactive renin in order to explain changes in plasma levels of the two forms of renin. 7. This paper supports the hypothesis that release of inactive renin by the kidney is controlled by a sodium-sensitive mechanism.

Animals↗
PubMed1992

Isolation and purification of a vascular hyperreactivity factor from rabbit kidney cortex.

A compound capable of amplifying the threshold pressor response to norepinephrine (NE) was obtained from rabbit kidney cortex. This compound was purified and characterized using a series of techniques including gel filtration, ion exchange chromatography, preparative electrofocusing, HPLC, FAB mass spectrometry (FAB-MS), and Fourier transform infrared spectrometry. From this, an acid/heat stable (6N HC1, 160 degrees C, 24 hours), low molecular weight (ca 147) compound with a strong (+) charge density (Pi greater than 10) was identified. When injected into assay rats (i.v.), this compound amplified the pressor response to fixed doses of NE. Taken together, this compound exhibits nearly identical characteristics (i.e. acid/heat stability, structure, charge and biologic activity to the naturally occurring polyamine spermidine (SPD-145.6 daltons). Moreover, bolus injections of SPD (10 micrograms, i.v.) amplified the pressor response to NE over a range of doses from 5-25 ng.

Animals↗
PubMed1979

Calcium ion transport across plasma membranes isolated from rat kidney cortex.

Basal-lateral-plasma-membrane vesicles and brush-border-membrane vesicles were isolated from rat kidney cortex by differential centrifugation followed by free-flow-electrophoresis. Ca2+ uptake into these vesicles was investigated by a rapid filtration method. Both membranes show a considerable binding of Ca2+ to the vesicle interior, making the analysis of passive fluxes in uptake experiments difficult. Only the basal-lateral-plasma-membrane vesicles exhibit an ATP-dependent pump activity which can be distinguished from the activity in mitochondrial and endoplasmic reticulum by virtue of the different distribution during free-flow electrophoresis and its lack of sensitivity to oligomycin. The basal-lateral plasma membranes contain in addition a Na+/Ca2+-exchange system which mediates a probably rheogenic counter-transport of Ca2+ and Na+ across the basal cell border. The latter system is probably involved in the secondary active Na+-dependent and ouabain-inhibitable Ca2+ reabsorption in the proximal tubule, the ATP-driven system is probably more important for the maintenance of a low concentration of intracellular Ca2+.

Adenosine Triphosphate↗
PubMed1985

ATP-dependent H+ pump in membrane vesicles from rat kidney cortex.

The presence of membrane vesicles containing an ATP-driven H+ pump was demonstrated in rat kidney cortex homogenate using the delta pH-sensitive dye acridine orange (AO). These vesicles were purified by differential and Percoll density gradient centrifugation. ATP-driven H+ uptake was about 20-fold enriched compared with the homogenate. Determination of marker enzyme activities indicated that these vesicles do not originate from brush border and basolateral membranes, lysosomes, endoplasmic reticulum, mitochondria, Golgi membranes, or red blood cells. The identity with brush border membranes was further excluded by the absence of Na+-H+ exchange. Renal cortical endocytotic vesicles that had taken up horseradish peroxidase or fluorescein isothiocyanate-labeled dextran (FITC-dextran) after injection of these substances into rats in vivo comigrated with the H+ pump activity on the Percoll gradient. Similar characteristics of the H+ pump demonstrated by the AO method and by fluorescence changes of in vivo trapped FITC-dextran proved the identity of H+ pump-containing vesicles with endocytotic vesicles. ATP-driven H+ uptake into endocytotic vesicles was stimulated by Cl- and weakly inhibited by oligomycin. N-ethylmaleimide, dicyclohexylcarbodiimide, and Dio-9 were stronger inhibitors. Histochemical studies revealed that horseradish peroxidase-filled endocytotic vesicles are localized in the apical region of proximal tubule cells. An H+ pump with similar characteristics, but much lower activity, was found in brush border membranes, basolateral membranes, and mitochondria isolated by standard techniques, suggesting a possible contamination of these preparations with endocytotic vesicles.

Acridine Orange↗
PubMed1988

In vitro loss of hydrophobicity of trehalase from the brush border membrane of rabbit kidney cortex.

Trehalase solubilized with 0.5% Triton X-100 and 0.5% deoxycholate from the brush border membrane of rabbit kidney cortex was all adsorbed on phenyl-Sepharose equilibrated with elution buffer containing no detergents, and all the adsorbed enzyme was eluted in one peak on the addition of 0.5% Triton X-100 to the elution buffer, in contrast to the results reported by Nakano and Sacktor (J. Biochem. 97, 1329-1335 (1985], who separated two forms of trehalase differing in hydrophobicity from rabbit kidney. On concentration of detergent-solubilized extracts, followed by incubation at 37 degrees C, however, there appeared trehalase nonadsorbable on phenyl-Sepharose, i.e. a hydrophilic trehalase. Various protease inhibitors added to the concentrated extracts did not inhibit this conversion at all. The concentration-incubation treatment also increased the proportion of trehalase that interacts with Con A-Sepharose. These results indicate that kidney trehalase that interacts with Con A-Sepharose. These results indicate that kidney trehalase is susceptible to some lytic action of a factor(s) intrinsic to the brush border membrane (limited autolysis), as seen with rabbit intestinal trehalase (Yokota et al., (1986) Biochim. Biophys. Acta 881, 405-414). Therefore, in studies of the molecular form of trehalase (and other proteins) in the brush border membrane of the kidney and intestine where a lot of hydrolases exist, it is very important to take account of limited autolysis which results in some chemical modifications without affecting enzymatic activity.

Animals↗
PubMed2002

DNase I-like endonuclease in rat kidney cortex that is activated during ischemia/reperfusion injury.

Ischemia/reperfusion is known to result in DNA fragmentation and cell death in kidney tubular epithelium, but the endonucleases responsible for this DNA damage have not been identified. DNA substrate gel analysis of extracts from normal rat kidney cortex revealed the presence of a DNase with an apparent molecular mass of 30 to 34 kD. This enzyme is not a dimer of the previously described nuclear 15-kD endonuclease in kidney cells. Partially purified DNase exhibited characteristics similar to those of rat DNase I. The DNase was able to digest circular DNA (endonuclease), required both Ca(2+) and Mg(2+) ions, and was inhibited by Zn(2+) and by aurintricarboxylic acid; it was not inhibited by G-actin. Rat kidneys were subjected to 40 min of ischemia, followed by 0, 1, 4, 16, or 48 h of reperfusion. The activity of the DNase in cytosolic and nuclear extracts, the 200-bp ladder-generating activity, and 3'OH strand breaks in nuclear DNA were simultaneously increased after ischemia, during the first hours of reperfusion. Oxidative DNA damage, measured as 8-hydroxydeoxyguanosine content, did not coincide with endonuclease-generated DNA breaks. Oxidative DNA damage was increased during ischemia and gradually decreased during reperfusion. Phosphorothioated DNase I antisense oligodeoxynucleotide introduced into cultured NRK-52E rat kidney epithelial cells inhibited DNA fragmentation and attenuated cell death induced by hypoxia/reoxygenation in vitro. The data indicate that the DNase I-like endonuclease may contribute to DNA fragmentation in reperfused rat kidneys.

Animals↗
PubMed1978

Characterization of the iron-sulfur protein of the mitochondrial outer membrane partially purified from beef kidney cortex.

The iron-sulfur protein present in the mitochondrial outer membrane has been partially purified from beef kidney cortex mitochondria by means of selective solubilization followed by DEAE-cellulose chromatography. The EPR spectrum of the iron-sulfur protein with g-values at 2.01, 1.94 and 1.89 was well resolved up to 200 K which is unusual for an iron-sulfur protein. Analyses confirmed a center with two iron and two labile sulfur atoms in the protein. By measuring the effect of oxidation-reduction potential on the EPR signal amplitude, midpoint potentials at pH 7.2 were determined both for the purified iron-sulfur protein, +75 (+/- 5) mV, and in prepared mitochondrial outer membrane, +62 (+/- 6) mV. At pH 8.2 slightly lower values were indicated, +62 and 52 mV, respectively. The oxidation-reduction equilibrium involved a one electron transfer. A functional relationship to the rotenone-insensitive NADH-cytochrome c oxidoreductase in the mitochondrial outer membrane is suggested. Both this activity and the iron-sulfur center were sensitive to acidities slightly below pH 7 in contrast to the iron-sulfur centers of the inner membrane.

Animals↗
PubMed1982

Phospholipid methylation of kidney cortex brush border membranes. Effect on fluidity and transport.

Exposure of intact brush border membrane vesicles of hog kidney cortex to cholesterol oxidase resulted in 24% oxidation of membrane cholesterol compared with more than 95% oxidation of cholesterol in lipids isolated from membranes, showing that cholesterol is asymmetrically distributed in membranes. Phospholipase C, hydrolyzed 76% of phosphatidylcholine and 10-12% phosphatidylethanolamine while phosphatidylserine was not hydrolyzed, thus indicating that majority of phosphatidylcholine is present on the outer surface of these vesicles while phosphatidylethanolamine and phosphatidylserine are present on the inner surface. Methylation of phospholipids in brush border membrane with S-adenosyl-[methyl-3H]methionine resulted in the formation of phosphatidyl-N-monomethylethanolamine, phosphatidyl-N,N]dimethylethanolamine and phosphatidylcholine from endogenous phosphatidylethanolamine. The Km for S-adenosylmethionine was 1.10(-4) M with an optimum pH 9.0 for the formation of all three methyl derivatives. Mg2+ was without any effect between pH 5 to 10. Addition of exogenous mono- and dimethylphosphatidylethanolamine derivatives enhanced methyl group incorporation by 4-5-fold as compared to the addition of phosphatidylethanolamine. The conversion of endogenous phosphatidylethanolamine to phosphatidyl-N-monomethylethanolamine or addition of exogenous phosphatidylmonomethylethanolamine to brush border membrane did not result in a change in bulk membrane fluidity as determined by fluorescence polarization of diphenylhexatriene. Methylation of phosphatidylethanolamine in brush border membrane did not affect the Na+-dependent uptake of either D-glucose or phosphate, although the accessibility of cholesterol in membrane to cholesterol oxidase was diminished by 21%, presumably due to altered flip-flop movement of cholesterol in the membrane.

Animals↗
PubMed1976

GAMMA-Glutamyl transpeptidase of sheep-kidney cortex. Isolation, catalytic properties and dissociation into two polypeptide chains.

Gamma-Glutamyl transpeptidase was isolated from sheep kidney cortex as an apparently homogeneous, highly active protein. At optimal pH and in the absence of acceptors, the enzyme catalyzes the release of about 510 mumol of p-nitroaniline per mg protein per min from the model substrate L-gamma-glutamyl-p-nitroanilide. Polyacrylamide gel electrophoresis in a sodium dodecylsulfate buffer system showed the presence of a large (Mr approximately 65000) and a small (Mr approximately 27000) polypeptide chain. Dissociation into two polypeptide chains was also achieved in 8 M urea. Amidination with dimethylsuberimidate produced a crosslinked protein of molecular weight approximately 90000. In the course of this work a convenient procedure was developed for the determination of gamma-glutamyl transpeptidase activity using L[glycine-2-3H]glutathione as the substrate. In this procedure the release of cysteinyl-[2-3H]glycine from glutathione is followed, after separation of the radioactive di-peptide from unreacted glutathione on a small Dowex-1 acetate column. The reactions with gamma-glutamyl-p-nitroanilide and glutathione are both strongly activated by several metal ions (Ca2+, Mg2+, Na+ and K+) and by a number of amino acids and peptide acceptors. The products of the reaction with glutathione were identified as cysteinylglycine, gamma-glutamylglutathione and glutamate. The formation of these products is consistent with the function of gamma-glutamyl transpeptidase in both the gamma-glutamyl transfer reaction and in the hydrolysis of the gamma-glutamyl bond. The activating effect of metal ions in the reaction with glutathione was shown to be dependent on the acceleration of the transfer reaction; the rate of hydrolysis of the gamma-glutamyl bond remaining unchanged.

Animals↗