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PubMed1985

Inhibitory effect on lithium on p-aminohippurate transport in rat kidney cortex in vitro.

The effect of lithium on p-aminohippurate (PAH) transport was studied using slices and basolateral membrane vesicles prepared from rat kidney cortex. The addition of lithium in concentrations ranging from 0.5 to 5 mM caused a concentration-dependent inhibition of PAH accumulation in the slices. Lithium inhibited PAH accumulation in the slices, not only during the rapid uptake period (after 10 min) but also during the approach to equilibrium (after 30 min). The effect of lithium (2 mM) in the slices was irreversible. The inhibitory effect of lithium was not the result of changes in the water distribution and the concentrations of ATP, sodium and potassium in the slices during incubation. The effect of lithium on the kinetic parameters for PAH accumulation was to decrease Vmax, while apparent Km remained constant. There was no lithium effect on the efflux of PAH from the slices back into the incubation medium, indicating that lithium inhibited PAH influx to the kidney cell. No evidence was obtained to indicate that lithium (1 mM) directly affected PAH uptake by isolated basolateral membrane vesicles. These results suggest that lithium seems to affect metabolism linked to the carriers for PAH transport other than ATP production and sodium gradient and then seems to decrease the mobility of the carriers in the membranes.

Adenosine Triphosphate↗
PubMed1988

Na-pump activity in rat kidney cortex cells and its relationship with the cell volume.

The present work was undertaken to evaluate whether changes in cell water content of rat kidney cortex cells can modulate the transport activity of the ouabain-insensitive Na pump as they modulate the ouabain-insensitive Na+-ATPase. It was found that there is a close relationship between the cell volume and activity of the Na pump, whereas Na,K-pump activity is not affected by variations in cell volume. When the cell water content is low, Na-pump activity (Na+ transport and Na+-ATPase activity) is minimal. Increases in cell water content produce a concomitant increase in Na-pump activity.

Adenosine Triphosphatases↗
PubMed1977

The influence of 3,4-dihydroxyphenylacetic acid on the accumulation of 5-hydroxyindoleacetic acid in the choroid plexus and kidney cortex slices of rats.

In vitro, the choroid plexus of rats accumulates 5-hydroxyindoleacetic acid (5-HIAA) by active transport. In the experiments presented here, the kidney cortex slices also showed active accumulation of this organic acid, which proved to be inhibited by most of the organic acids tested. In the choroid plexus 3,4-dihydroxyphenylacetic acid (DOPAC), a metabolite of dopamine, stimulated the accumulation of 5-HIAA, whereas in the kidney slices DOPAC was inhibitory. This stimulating effect of DOPAC was blocked by homovanillic acid and probenecid. Metabolic inhibitors such as 2,4-dinitrophenol and N-ethylmaleimide also blocked the stimulation, but sodium fluoride was ineffective. Omission of calcium, but not magnesium ion in the incubation medium depressed the accumulation of 5-HIAA. DOPAC still produced the stimulating action in calcium-free medium. The release of 5-HIAA from choroid plexus was retarded by DOPAC. These results suggest that the stimulating action of DOPAC may be due to a calcium-dependent active transport system and delay of 5-HIAA release.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Expression cloning of a cDNA from rabbit kidney cortex that induces a single transport system for cystine and dibasic and neutral amino acids.

We have isolated a cDNA clone by screening a rabbit kidney cortex cDNA library for expression of sodium-independent transport of L-arginine and L-alanine in Xenopus laevis oocytes. Expressed uptake relates to a single component of sodium-independent transport for dibasic and neutral amino acids. This transport activity resembles the functionally defined system b0,+ and carries cystine and dibasic amino acids with high affinity. The rBAT (b0,+ amino acid transporter-related) mRNA is found mainly in kidney and intestinal mucosa. It encodes a predicted 77.8-kDa protein with only one putative transmembrane domain and seven potential N-glycosylation sites. This protein could either be a constitutive element or a specific activator of system b0,+.

Amino Acid Sequence↗
PubMed2001

Na(+)-dependent D-mannose transport at the apical membrane of rat small intestine and kidney cortex.

The presence of a Na(+)/D-mannose cotransport activity in brush-border membrane vesicles (BBMV), isolated from either rat small intestine or rat kidney cortex, is examined. In the presence of an electrochemical Na(+) gradient, but not in its absence, D-mannose was transiently accumulated by the BBMV. D-Mannose uptake into the BBMV was energized by both the electrical membrane potential and the Na(+) chemical gradient. D-Mannose transport vs. external D-mannose concentration can be described by an equation that represents a superposition of a saturable component and another component that cannot be saturated up to 50 microM D-mannose. D-Mannose uptake was inhibited by D-mannose >> D-glucose>phlorizin, whereas for alpha-methyl glucopyranoside the order was D-glucose=phlorizin >> D-mannose. The initial rate of D-mannose uptake increased as the extravesicular Na(+) concentration increased, with a Hill coefficient of 1, suggesting that the Na(+):D-mannose cotransport stoichiometry is 1:1. It is concluded that both rat intestinal and renal apical membrane have a concentrative, saturable, electrogenic and Na(+)-dependent D-mannose transport mechanism, which is different from SGLT1.

Animals↗
PubMed1986

Transport of organic cations in brush border membrane vesicles from rabbit kidney cortex.

The transport of three organic cations, tetraethylammonium (TEA), morphine and N1-methylnicotinamide (NMN) was studied in brush border membrane vesicles from rabbit kidney cortex under voltage clamp conditions. A proton gradient (pHi = 6.0, pHo = 7.4) produced a large stimulation of TEA and morphine uptake, yielding a transient overshoot of 190 and 220% respectively, as compared to equilibrium uptake values. No overshoot was observed under pH equilibrium conditions (pHi = pHo = 7.4, control). These data suggest the presence of a proton-organic cation exchange mechanism in the rabbit renal cortical brush border membrane. Identical experimental conditions (proton gradient) failed however to stimulate significantly NMN transport above control values measured under pH equilibrium conditions. Proton gradient driven TEA transport showed an inhibition of 21% in the presence of NMN (1 mM) and of 63% in the presence of TEA (1 mM), and TEA transport was stimulated by preloading the vesicles with 1 mM TEA (305%) but not with 1 mM NMN (128%). NMN transport showed an inhibition of 39% in the presence of 1 mM TEA and of 27% in the presence of 1 mM NMN and its transport was stimulated by preloading the vesicles with 1 mM TEA (228%) and 1 mM NMN (178%). Our data suggest that TEA, NMN and morphine are transported by a common transport mechanism for which NMN has only a low affinity.

Animals↗
PubMed1985

Ion transport and oxygen consumption in kidney cortex slices from young and old rats.

The effects of aging on active Na+ extrusion and oxygen consumption associated with it were studied in rat kidney cortex cells. It was found that (a) the active extrusion of Na+ undergoing Na/K exchange and the active extrusion of Na+ with Cl- and water were diminished in old rats (24 months) as compared with young rats (3 months); (b) the oxygen consumption associated with each of the two active mechanisms of Na+ extrusion was also diminished in the old rats; (c) the calculated turnover rate of the Na/K pump was significantly lower for the old rats.

Aging↗
PubMedDate not supplied

Cadmium levels in the lung, liver, kidney cortex, and urine samples from Australians without occupational exposure to metals.

The authors undertook this study to assess levels of cadmium exposure in the general population. Samples of lung, liver, and kidney were obtained from 61 cadavers (43 males, 18 females; 2-89 yr of age, mean age = 38.5 yr) who died from accidental causes and who were subject to postmortem examinations at the John Tonge Centre for Forensic Sciences, Queensland Health Scientific Services, Brisbane, Australia, in 1997 and 1998. Samples of bladder urine were also obtained from 22 cadavers. Tissue and urine samples were analyzed for cadmium, zinc, and copper with inductively coupled plasm (ICP) mass spectrometry. The overall mean values for cadmium in the lung, liver, and kidney cortex samples were 0.13, 0.95, and 15.45 microg/gm wet tissue weight. The average renal cadmium level in subjects with high lung-cadmium levels (n = 13) was 6 microg/gm wet tissue weight higher than that of similarly aged subjects who had medium lung-cadmium levels (n = 30). In females, the average level of cadmium in the liver was 74% greater than in males, and the average liver cadmium in females with high lung-cadmium levels was 100% higher than in males in the same age range who had the same high lung-cadmium levels. Renal cadmium accumulation tended to be greater in females than in males who were in the same age range and who had similar lung-cadmium levels, a result that suggested that there was a higher absorption rate of cadmium in females. The mean value for a urinary cadmium excretion of 2.30 microg/gm creatinine was found in a subset of samples that had a mean age of 39 yr and a renal cortex cadmium concentration of 18.6 microg/gm wet tissue weight. Urinary cadmium excretion rates were correlated more strongly with lung and kidney cadmium content than with age or liver cadmium levels. The results suggest that urinary cadmium excretion may be increased in smokers and could provide some estimate of body cadmium burdens in future Australian epidemiological studies.

Adult↗
PubMed1991

P-aminohippurate accumulation in kidney cortex slices: stimulation by dicarboxylates, amino acids and their oxoanalogues.

The effect of various amino acids and oxoacids on the accumulation of PAH in rat kidney cortex slices was determined. The following compounds were found to increase the PAH tissue to medium ratio (T/MPAH): a) dicarboxylic acids: glutarate, 2-oxoglutarate and oxaloacetate, b) amino acids: glutamate, isoleucine, leucine, valine, methionine, tryptophane, histidine, threonine and glycine, c) monocarboxylates: hydroxymethionine, oxovaline, oxoisoleucine and oxoleucine. There were no marked concentration/effect differences to glycine, glutamate, glutarate and oxovaline. Ouabain inhibited T/MPAH only slightly, but abolished its increase by pyruvate, 2-oxoglutarate and histidine. Oxygen hyposaturation abolished the T/MPAH increase caused by 2-oxoglutarate, pyruvate, glutamate and histidine. It is concluded that various substrates stimulating the organic anion transport system (OATS) do so namely by improving the energy supply, although the direct participation of dicarboxylates in OATS could be of relevance namely in short-lasting variations.

Amino Acids↗
PubMed1983

The subcellular distribution and storage form of renin in human kidney cortex.

An assay with the cation exchange resin Dowex 50 WX2 was developed and validated for the measurement of renin activity in subcellular fractions of kidney cortex. After differential centrifugation, renin was found predominantly in the soluble (SOL) fraction (70%) and to a lesser extent in the heavy mitochondrial (HM) extract (17%). Neither acid pH nor trypsin treatment increased renin activity in these fractions. Discontinuous and continuous sucrose concentration gradients were used to partially resolve renin-containing organelles in the granular moiety from marker enzymes for mitochondria, lysosomes, plasma membranes and peroxisomes. The molecular weight (MW) of renin in both the SOL and HM was approximately 45 000. No acid or trypsin-activatable forms of renin were found after gel filtration of these extracts. When renal cortical tissue was extracted in the presence of the proteolytic enzyme inhibitors N-ethylmaleimide (NEM), ethylenediaminetetraacetic acid (EDTA), aprotinin, phenylmethylsulfonyl fluoride (PMSF), benzamidine and pepstatin, renin activity was not increased by added trypsin. After gel filtration of the homogenates, the MW of renin activity was 45 000. Protease inhibitors did not appear to preserve high molecular weight (HMW) forms and no trypsin-activatable renin was found. These results suggest that in man renal renin is stored within mechanically fragile granules and that the major storage form is of low molecular weight (LMW).

Centrifugation, Density Gradient↗
PubMed1986

Inhibition by cyclic GMP of p-aminohippurate uptake by basolateral membrane vesicles isolated from rat kidney cortex.

We studied the effect of cyclic guanosine 3',5'-monophosphate (cyclic GMP) on p-aminohippurate (PAH) uptake by basolateral membrane vesicles isolated from rat kidney cortex. Cyclic GMP inhibited PAH uptake dose-dependently. Dibutyryl cyclic GMP inhibited the uptake of PAH to the same extent. However, cyclic adenosine 3',5'-monophosphate, cyclic cytidine 3',5'-monophosphate and guanosine monophosphate had no effect on PAH uptake by membrane vesicles. Therefore, the inhibition of PAH uptake was specific to cyclic GMP and not common to nucleotides. In the presence of probenecid, an inhibitor of PAH transport, cyclic GMP did not affect PAH uptake. Thus, cyclic GMP had an inhibitory effect on probenecid-sensitive PAH transport. Inhibition by cyclic GMP of PAH uptake by basolateral membrane vesicles as described this study may contribute to the decrease in PAH accumulation in kidney cortical slices caused by the cyclic nucleotide which we previously reported.

Aminohippuric Acids↗
PubMed1977

Effect of salt loading in the rat on adenylate cyclase and phosphodiesterase activity in kidney cortex, medulla and papilla.

Adenylate cyclase (AC) and phosphodiesterase (PDE) activities were studied in the cortex, medulla and papilla of the rat kidney. Sodium loading in vivo for 14 days resulted in a decrease of AC activity in the cortex, a small increase in the medulla and a substantial increase of AC activity in the papilla. Sodium loading caused reciprocal effects on PDE activity: an increase in kidney cortex and a decrease in kidney papilla. Loading of glucose in vivo or chronic administration of antidiuretic hormone in vivo did not cause the changes in AC or PDE observed after sodium loading. The possible significance of these findings is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1989

D-aspartate oxidase in rat, bovine and sheep kidney cortex is localized in peroxisomes.

D-Aspartate oxidase (EC 1.4.3.1) was assayed in subcellular fractions and in highly purified peroxisomes from rat, bovine and sheep kidney cortex as well as from rat liver. During all steps of subcellular-fractionation procedures, D-aspartate oxidase co-fractionated with peroxisomal marker enzymes. In highly purified preparations of peroxisomes, the enrichment of D-aspartate oxidase activity over the homogenate is about 32-fold, being comparable with that of the peroxisomal marker enzymes catalase and D-amino acid oxidase. Disruption of the peroxisomes by freezing and thawing released more than 90% of the enzyme activity, which is typical for soluble peroxisomal-matrix proteins. Our findings provide strong evidence that in these tissues D-aspartate oxidase is a peroxisomal-matrix protein and should be added as an additional flavoprotein oxidase to the known set of peroxisomal oxidases.

Amino Acid Oxidoreductases↗
PubMed1996

Purification and kinetic properties of a D-amino-acid peptide hydrolyzing enzyme from pig kidney cortex and its tentative identification with renal membrane dipeptidase.

We previously reported the presence of an enzyme activity which hydrolyzes Gly-D-Asp in pig kidney cortex. In the present study, an enzyme which hydrolyzes this peptide and other peptides having a low number of D- and L-amino acids has been purified from the brush border membranes of the same tissue. The native enzyme, having a molecular weight of 99,000, was apparently a homodimer of a subunit with a molecular weight of 48,000 and its optimum pH was 7.8 with Gly-D-Ala as substrate. The enzyme hydrolyzed many dipeptides, but not most of the tripeptides tested with a few exceptions, from which the carboxyl-terminal amino acid was liberated by the enzyme. Of the dipeptides examined, those having a D-amino acid at the amino-terminal were poor substrates, whereas those bearing a D-amino acid at the carboxyl-terminal were good substrates, comparable with their diastereomers with a L-amino acid at the same position. The enzyme was potently inhibited by cilastatin but not by amastatin and bestatin. Metal ion chelators and dithiothreitol were also inhibitory. Comparison of the properties of present enzyme with those of other known enzymes suggests that this should be tentatively identified with renal membrane dipeptidase. The demonstrated high activity toward dipeptides containing various D-amino acids at the carboxyl-terminal suggests a possibility that the enzyme in fact plays a role in degradation in vivo of D-amino-acid-containing peptides.

Animals↗
PubMed1982

Ouabain-insensitive Na+-stimulated ATPase activity of basolateral plasma membranes from guinea-pig kidney cortex cells. II. Effect of Ca2+.

The ouabain-insensitive, Mg2+-dependent, Na+-stimulated ATPase activity present in fresh basolateral plasma membranes from guinea-pig kidney cortex cells (prepared at pH 7.2) can be increased by the addition of micromolar concentrations of Ca2+ to the assay medium. The Ca2+ involved in this effect seems to be associated with the membranes in two different ways: as a labile component, which can be quickly and easily 'deactivated' by reducing the free Ca2+ concentration of the assay medium to values lower than 1 microM; and as a stable component, which can be 'deactivated' by preincubating the membranes for periods of 3-4 h with 2 mM EDTA or EGTA. Both components are easily activated by micromolar concentrations of Ca2+. The Ka of the system for Na+ is the same, 8 mM, whether only the stable component or both components, stable and labile, are working. In other words, the activating effect of Ca2+ on the Na+-stimulated ATPase is on the Vmax, and not on the Ka of the system for Na+. The activating effect of Ca2+ may be related to some conformational change produced by the interaction of this ion with the membranes, since it can also be obtained by resuspending the membranes at pH 7.8 or by ageing the preparations. Changes in the Ca2+ concentration may modulate the ouabain-insensitive, Na+-stimulated ATPase activity. This modulation could regulate the magnitude of the extrusion of Na+ accompanied by Cl- and water that these cells show, and to which the Na+-ATPase has been associated as being responsible for the energy supply of this mode of Na+ extrusion.

Animals↗
PubMed1978

[Repartition of the kidney cortex glomerulus in rats].

This paper presents the repartition of 989 glomeruli in 8 parallel concentric renal cortex zones, by projecting on a calibrated screen rat kidney slices photographies. The glomerular density increases regularly from the outside to the middle cortical zones and then decreases to the deepest juxtamedullary zones.

Animals↗
PubMed1990

Arachidonic acid epoxygenase. Stereochemical analysis of the endogenous epoxyeicosatrienoic acids of human kidney cortex.

Mass spectral and chromatographic analysis demonstrates the presence of 14,15-, 11,12- and 8,9-epoxyeicosatrienoic acids (44%, 33% and 23% of the total, respectively) in human kidney cortex. Chiral analysis of the human renal epoxyeicosatrienoic acids shows the formation of 8,9-, 11,12- and 14,15-epoxyeicosatrienoic acids in a 1:1, 4:1 and 2:1 ratio of antipodes, respectively. These results demonstrate the biosynthetic origin of the human kidney 11,12- and 14,15-epoxyeicosatrienoic acids and suggest a role for renal cytochrome P-450 in the bioactivation of endogenous pools of arachidonic acid.

8,11,14-Eicosatrienoic Acid↗
PubMed1981

Effect of genetic diabetes on beta-N-acetylglucosaminidase activity in plasma, conjunctiva, muscle and kidney cortex of mice.

The activity of beta-N-acetylglucosaminidase, a lysosomal enzyme concerned with the degradation of glycoproteins and mucopolysaccharides, in plasma, conjunctiva, thigh muscle and kidney cortex of normal Swiss Albino and genetically diabetic KK mice of 20, 40, 70, 180 and 360 days of age was determined. The enzyme activity was significantly lower in the tissues of the KK mice of 180 and/or 360 days of age when compared with age-matched Swiss Albino mice. This lower enzyme activity was considered to be a reflection of the changes in the glycoprotein and basement membrane metabolism of these tissues.

Acetylglucosaminidase↗