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PubMed2005

The role of intracellular cAMP in renal gluconeogenesis in view of differential action of various cAMP analogues.

Effects of various cAMP analogues on gluconeogenesis in isolated rabbit kidney tubules have been investigated. In contrast to N(6),2'-O-dibutyryladenosine-3',5'-cyclic monophosphate (db-cAMP) and cAMP, which accelerate renal gluconeogenesis, 8-bromoadenosine-3',5'-cyclic monophosphate (Br-cAMP) and 8-(4-chlorophenylthio)-cAMP (pCPT-cAMP) inhibit glucose production. Stimulatory action of cAMP and db-cAMP may be evoked by butyrate and purinergic agonists generated during their extracellular and intracellular metabolism resulting in an increase in flux through fructose-1,6-bisphosphatase and in consequence acceleration of the rate of glucose formation. On the contrary, Br-cAMP is poorly metabolized in renal tubules and induces a fall of flux through glyceraldehyde-3-phosphate dehydrogenase. The contribution of putative extracellular cAMP receptors to the inhibitory Br-cAMP action is doubtful in view of a decline of glucose formation in renal tubules grown in the primary culture supplemented with forskolin. The presented data indicate that in contrast to hepatocytes, in kidney-cortex tubules an increased intracellular cAMP level results in an inhibition of glucose production.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1997

Inhibition and restimulation by insulin of cellular autophagy in distal tubular cells of the kidney in early diabetic rats.

Cellular autophagy in the cells of distal tubular segments (DT cells) of the kidney cortex in streptozotocin-diabetic rats was evaluated by quantitative electron microscopy. Five days after streptozotocin administration, volume and numerical densities of autophagic vacuoles (AVs) in DT cells were reduced by 56 and 57%, respectively. The correction of the diabetic state by insulin injection reversed the inhibition of cellular autophagy. Volume and numerical densities of AVs increased by 97 and 53%, respectively. Endogenous insulin replacement by islet transplantation showed the same effect on cellular autophagy. Volume and numerical densities of AVs increased by 82 and 34%, respectively, as compared with sham-operated diabetic animals. The data show that, during diabetic kidney hypertrophy, the cellular autophagy is inhibited in DT cells to the same extent as in proximal tubular cells, suggesting that DT cells contribute in a balanced manner to hypertrophic growth of the kidney cortex. Similarly, DT cells are involved in the catabolic reaction, i.e., stimulation of autophagy, after metabolic correction of the diabetic state by insulin.

Animals↗
PubMed1975

Renal cortex guanylate cyclase. Preferential enrichment in glomerular membranes.

1. The localisation and some of the properties of rabbit kidney cortex guanylate cyclase (GTP pyrophosphatase lyase (cyclizing) EC 4.6.1.2) have been studied. Upon fractionation of dissociated renal cortex, guanylate cyclase activity was preferentially enriched in fractions of pure glomeruli, where its specific activity was 44.5 times that measured in tubular fragments. Most, if not all, of the glomerular activity was found to be firmly membrane-bound, whereas the guanylate cyclase activity of the tubules was mainly soluble. Therefore, particulate guanylate cyclase activity could serve as marker enzyme for kidney glomeruli. 2. All hormones or hormone-like agents tested were without effect on kidney guanylate cyclase activity. Triton X-100 stimulated both glomerular and tubular activity. 3. Considering the high cyclic GMP forming capacity of kidney glomeruli, part of the cyclic GMP found in urine might be synthetized locally in these structures.

Animals↗
PubMed1993

Developmental expression of acid-base-related proteins in the rabbit kidney.

The newborn is limited in its ability to respond to acid-base perturbations. To investigate the development of renal H+/HCO3- transport mechanisms, we probed acid-base-related epitopes in the mesonephric and developing metanephric kidneys of rabbits. Using immunofluorescence with monoclonal antibodies to the vacuolar H+ATPase, band 3-like Cl-/HCO3- exchanger, and apical surface of fully differentiated beta-intercalated cells, and peanut lectin cytochemistry (another marker of beta-intercalated cells), we found that these epitopes were poorly expressed in the nephrogenic zone of the newborn kidney cortex. Deeper in the cortex, collecting ducts showed weak apical staining with beta-intercalated cell antibodies and two patterns of staining with the H+ATPase and band 3 antibodies: polar and circumferential or diffuse. Some cells showed apical staining with H+ATPase while others showed diffuse staining, similar to that observed in the mature cortical collecting duct. Band 3 labeling was basolateral, as observed in the adult, and diffuse, which was rarely seen in mature kidney sections. Newborn outer medullary collecting ducts showed apical labeling with H+ATPase and basolateral staining with band 3 antibodies, similar to the mature outer medulla. Surprisingly, the mesonephric collecting tubule showed cells with apical H+ATPase staining or basolateral band 3 labeling and, less frequently, cells with positive staining for beta-intercalated cells. The relative maturity of the mesonephric collecting tubule and similarity to what is observed in mature metanephric collecting ducts indicates that intercalated cells may be present and functioning in both organs. Thus, the lineage of intercalated cells may be more intricate than previously believed.

Aging↗
PubMed1978

Maturation of p-aminohippuric acid transport in the developing rabbit kidney: interrelationships of the individual components.

The excretion of both endogenous organic (aryl) acids, such as benzoic acid, and exogenous ones, such as p-aminohippuric acid (PAH), penicillin, and furosemide, is reduced in the human neonate and other immature animals. The unique developmental pattern of aryl acid transport in immature rabbit kidney cortex slices is produced by the interrelationships of PAH uptake, efflux, and amount of intracellular binding protein, all of which reach mature levels at different ages.

Aminohippuric Acids↗
PubMed1994

Low-Pi diet increases the abundance of an apical protein in rat proximal-tubular S3 segments.

Dietary phosphate (Pi) restriction is associated with an adaptive increase in proximal-tubular apical brush-border membrane (BBM) sodium-dependent Pi transport (Na-Pi cotransport). Adaptation to Pi restriction is dependent on de novo protein synthesis; however, it is not known whether the proteins involved represent newly synthesized Na-Pi cotransporters or some other (regulatory) proteins. Recently the cDNA for a Na-Pi cotransport system of rabbit kidney cortex (system NaPi-1) has been identified by expression cloning. The purpose of this study was to determine if the adaptive increase in Na-Pi cotransport in response to dietary Pi restriction in the rat is associated with an increase in the abundance of a NaPi-1-related protein. To answer this question we took advantage of the cross-reactivity of polyclonal antibodies raised against a C-terminal peptide of the NaPi-1 protein with a protein of BBM isolated from rat kidney cortex. On Western blots, a positive reaction with a protein with an apparent molecular mass of 100 kDa was observed in BBM isolated from juxtamedullary cortex and, to a lesser extent, in BBM isolated from superficial cortex. In immunohistochemical studies anti-(NaPi-1)-antiserum-mediated immunofluorescence was observed predominantly in S3 segments where the immunoreaction was restricted to the brush borders. Compared to control BBM, in BBM isolated from the juxtamedullary cortex of rats fed a low-Pi diet, there was a twofold increase in the abundance of the 100-kDa protein. In the same membrane vesicles Na-Pi cotransport was increased threefold. The results of this study demonstrate specific expression of a 100-kDa apical protein in S3 cells of rat proximal tubules. Increased abundance of the 100-kDa protein due to chronic Pi restriction suggests an involvement of this protein in the (chronic) adaptive response of S3 cells to a low-Pi diet.

Adaptation, Physiological↗
PubMed1986

Pipecolic acid is oxidized by renal and hepatic peroxisomes. Implications for Zellweger's cerebro-hepato-renal syndrome (CHRS).

Increased levels of pipecolic acid have been reported in patients with cerebro-hepato-renal syndrome (CHRS) of Zellweger and the general deficiency of peroxisomal function has been implicated in its pathogenesis. We have therefore investigated the capacity of normal peroxisomes to metabolize pipecolic acid. Highly purified peroxisomes were obtained from rat liver and rat and beef kidney cortex by a recently developed method using metrizamide gradients and a vertical rotor. These preparations oxidized D,L-pipecolic acid as evidenced by the measurement of H2O2 production. Incubation with either the D- or L-isomer revealed that almost exclusively D-pipecolate is oxidized. The specific activities proved to be 20-50 times higher in renal than in hepatic peroxisomes. A commercially available crystalline suspension of D-amino acid oxidase from porcine kidney also oxidized the pipecolic acid with the following rates 54:36:1 respectively for D-:,D,L-:L-isomers. Incubation of vibratome sections of rat kidney and liver in a medium containing D-pipecolic acid and cerous ions, revealed electron-dense deposits over the matrix of peroxisomes confirming the localization also by fine structural cytochemistry. These observations demonstrate the capability of mammalian peroxisomes to oxidize pipecolic acid and suggest that the absence or deficiency of peroxisomal D-amino acid oxidase may be implicated in the pathogenesis of hyperpipecolatemia in Zellweger's CHRS.

Abnormalities, Multiple↗
PubMed2006

Novel approaches to analyse glomerular proteins from smallest scale murine and human samples using DIGE saturation labelling.

Loss of renal function is often associated with the injury of kidney glomeruli. It is therefore necessary to understand the mechanisms leading to progressive glomerular diseases; this may be addressed using proteomics. Until now, however, analysis of the glomeruli proteome using 2-DE has been technically hampered by low protein yields from scarce samples. To circumvent this problem, we developed a procedure which allows the human and mouse glomeruli proteome to be analysed. In this study, two different approaches were used to isolate mouse and human glomerular protein from kidney cortex. Mouse glomeruli were extracted by embolisation magnetic beads into the glomerular capillaries. Laser capture microdissection (LCM) was utilised to harvest glomeruli from human biopsy material. Human and murine samples were analysed using a fluorescence saturation labelling technique. Using 3 microg mouse glomerular protein a total of 2900 spots were resolved for differential proteome analysis. Moreover, it was also demonstrated for the first time that only ten glomeruli (0.5 microg) picked by LCM from a slide of a human kidney biopsy material were sufficient to visualise 900 spots. This novel strategy paves the way for future experiments aimed at investigating functional proteomics of glomerular diseases in humans and in mice.

Animals↗
PubMed1993

Effect of low-phosphate diet on sodium/phosphate cotransport mRNA and protein content and on oocyte expression of phosphate transport.

Recently, we have isolated a complementary DNA most likely related to rabbit kidney cortex brush border membrane sodium/phosphate (Na/Pi) cotransport activity [NaPi-1 (1)]. To further elucidate the cellular mechanisms involved in dietary 'adaptation' of renal Na/Pi cotransport, we have exposed young rabbits for 2 weeks to either a low phosphate (Pi) diet (LPD) or a high Pi diet (HPD). Initial linear uptake of Na/Pi cotransport in isolated brush border membrane vesicles was increased in rabbits on a LPD compared with those on a HPD. Injection of equal amounts of total mRNA isolated from kidney cortex of LPD or HPD rabbits into Xenopus laevis oocytes resulted in a higher stimulation of Na-dependent oocyte Pi uptake in LPD than HPD preparations. No difference in the content of 'specific' mRNA (NaPi-1 cDNA probe, Northern blots) and of the content of the 'specific' brush border membrane protein (NaPi-1 antipeptide antibody, Western blots) between LPD and HPD preparations was observed. We conclude that 'chronic' dietary Pi deprivation leads to a protein synthesis-dependent alteration of Na/Pi cotransport activity which does not involve a change in the total amount of a protein related to the recently cloned NaPi-1 protein.

Animals↗
PubMed1991

Distribution of pyruvate carboxylase along the rat nephron: an immunological and enzymatic study.

Antibodies against purified rat-kidney-cortex pyruvate carboxylase were raised in rabbits. These polyspecific antibodies recognize pyruvate carboxylase enzymes alone without cross reactivity with other carboxylases as detected by immunoblotting. The abundance of pyruvate carboxylase in the various renal fractions was measured by ELISA and its activity by the fixation of [14C]CO3H-. The results were corroborated by a combination of immunocytochemistry and transmission electron microscopy. A good correlation was found between the enzymatic activity and the quantity of enzyme contained in each fraction. The kidney-cortex pyruvate carboxylase was primarily located in proximal tubules, in accord with its important role in gluconeogenesis.

Animals↗
PubMed1998

Characterization of the 5'-flanking region of OK cell type II Na-Pi cotransporter gene.

The renal type II Na-Pi cotransport is the rate-limiting step in proximal tubular phosphate (Pi) reabsorption. Among the different "proximal tubular" cell lines, this transporter seem only to be expressed in opossum kidney cells (OK cells). We have isolated the 5'-flanking region of the ok-Npt2 gene (OK cell type II Na-Pi cotransporter) including exons 1-3 and containing a TFIID site (TATA box), a GCCAAT site, an AP1 site, and two microsatellite GGAA repeats. Major transcription initiation sites were determined by primer extension and rapid amplification of 5' cDNA ends (5'-RACE). A 327-bp fragment containing the TFIID and GCAAT element was driving the downstream luciferase reporter gene in homologous transfection assays. Slightly reduced promoter activity was observed with a 198-bp fragment containing the GCAAT element; shorter fragments were without activity. Promoter activity (327-bp fragment) could also be observed in transfections into HeLa cells but not in U937 human macrophage cells, MCT mouse kidney cortex cells, and MDCK cells. Different "physiological" stimuli known to be associated with altered proximal tubular Na-Pi cotransport activity are without effect on transcriptional activity in above homologous transfection experiments.

Animals↗
PubMed1980

Evidence that kidney lysosomal proteinases degrade the collagen of glomerular basement membrane.

Three thiol-dependent tissue proteinases have been isolated from human kidney cortex by methods using detergent extraction, gel chromatography, affinity chromatography and separation by ion-exchange. The properties of each enzyme toward several chromogenic low molecular weight substrates, azocasein and collagen indicate that they are similar to cathepsins B, H and L. All three enzymes degrade glomerular basement membrane at acid pH. Cathepsin B and L were particularly active against glomerular basement membrane. It has been demonstrated that in liver these enzymes exist together in lysosomes. These properties indicate that the kidney thiol proteinases may be an important factor in the turnover of glomerular basement membrane.

Basement Membrane↗
PubMed1993

Upregulation of renal endothelin receptors in glycerol-induced acute renal failure in the rat.

Acute renal failure was induced in rat with a hypertonic glycerol solution and endothelin-1 (ET-1) binding was measured in kidney membrane preparations. In control animals, [125I]-ET-1 bound to specific recognition sites in kidney cortex (Bmax = 134 +/- 11 fmol/mg protein) and medulla (Bmax = 300 +/- 9 fmol/mg protein) with an apparent dissociation constant (Kd) of 0.16 +/- 0.06 nM and 0.39 +/- 0.07 nM for cortex and medulla, respectively. A single i.m. dose of 10 ml/kg glycerol (50% w/v) resulted in alterations of renal function that were maximal 48 h after glycerol administration. After this 48-h period, serum urea was increased from 0.20 +/- 0.01 g/L to 1.16 +/- 0.20 g/L (p < 0.001) and creatinine clearance was reduced from 1.04 +/- 0.15 ml/min to 0.23 +/- 0.06 ml/min (p < 0.001). Renal ET-1 receptor density was significantly increased in glycerol-treated rats to 255 +/- 14 fmol/mg protein in renal cortex (p < 0.01), and 576 +/- 55 fmol/mg protein in renal medulla (p < 0.01), with no significant modification of the Kd values. These results suggest that upregulation of ET-1 receptors is involved in renal hemodynamic impairment induced by glycerol.

Acute Kidney Injury↗
PubMed1991

Identification and localization of pertussis toxin-sensitive GTP-binding proteins in bovine kidney glomeruli.

The vascular tree and the mesangium in the glomerulus respond to various hormones, growth factors, and autonomic signals, leading to generation of second messengers and regulation of ion channels. Guanine nucleotide regulatory proteins (G proteins) mediate these effects in other systems. Glomerular G proteins were studied by immunoblotting and immunohistochemical techniques. Glomeruli were isolated from bovine kidney cortex by differential sieving. Glomerular proteins were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and nitrocellulose transfers were immunoblotted with antibodies to G proteins. G alpha,common antiserum (P-960) recognized proteins with a molecular mass of 41 to 45 kDa. Antibodies against peptide sequences specific to Gi alpha and Go alpha demonstrated Gi alpha, 1/3 (molecular mass, 39 to 41 kDa), Gi alpha 2 (molecular mass, 40 kDa), and Go alpha (molecular mass, 39 kDa). Presence of these proteins was further confirmed by pertussis toxin-catalyzed ADP ribosylation of protein(s) with a molecular mass of 39 to 41 kDa in the glomeruli. Immunohistochemical staining of frozen sections from bovine kidney cortex revealed the presence of Gi alpha 2 in capillary loop distribution in glomeruli and interstitium, but Gi,1/3 or Go could not be demonstrated. The pattern of immunofluorescence with Gi alpha 2 antiserum suggested localization of Gi alpha 2 to the endothelium in glomerular and interstitial vasculature. The novel finding of Go in glomeruli requires localization of Go to specific cells and determination of its role in glomerular physiology. In conclusion, these studies demonstrate that bovine kidney glomeruli express alpha subunits of pertussis toxin-sensitive GTP-binding proteins Gi,1/3, Gi,2 and Go.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate Ribose↗
PubMed1995

Decreased cyclic inositol phosphohydrolase activity in hamster renal tumors and human renal cell carcinomas.

Cyclic inositol phosphohydrolase (cIPH) (EC 3.1.4.36) hydrolyzes the cyclic phosphodiester bond of cyclic inositol monophosphate to yield inositol 1-phosphate. Renal tissue in various species has been shown to contain the highest activity of this enzyme. Cyclic inositol monophosphate, the substrate for this enzyme, has been implicated in the regulation of cell density. Thus, we determined whether activity of this enzyme is modulated in renal tumor. Samples of hamster renal tumors induced by diethylstilbestrol (DES) demonstrated 87% less cIPH activity than control hamster kidney. After 8 days of DES treatment of hamsters, a 28% decrease in the cIPH activity in kidney was observed. Interestingly, comparison of the cIPH activity in normal human kidney cortex, medulla, and renal cell carcinoma gave the following values (mean +/- SD), 10.6 +/- 4.6 (9), 6.7 +/- 4.6 (5), and 1.9 +/- 2.3 (8), respectively. Our study demonstrates that cIPH activity is reduced in hamster and human renal tumors.

Animals↗
PubMedDate not supplied

Renal developmental delay expressed by reduced glomerular number and its association with growth retardation in victims of sudden infant death syndrome and in "normal" infants.

In victims of sudden infant death syndrome (SIDS), renal development has been reported to be significantly impaired. In the present study, we used stereological techniques to estimate volume of kidney cortex and total number of glomeruli in a group of human infants. Infants were classified according to cause of death-SIDS or non-SIDS. Cases were further subdivided according to birth weight-normal birth weight (NBW) or low birth weight (LBW) (we were unable to identify any non-SIDS LBW infants for our study). No significant differences were found between NBW and LBW infants (irrespective of cause of death) for cortical volume, glomerular density, or total glomerular number (p > 0.140). Kidney cortical volume, glomerular density, and total glomerular number were not significantly different between SIDS and non-SIDS infants (p > 0.510). Glomerular number was only significantly less in SIDS infants of LBW (p = 0. 032) than in controls according to the Wilcoxon rank sum test; using the Kruskal-Wallis for one-way analysis, no significant difference was found (p > 0.010). These results contrast with those from previous studies, as a reduction in glomerular number was not noted in SIDS NBW infants, and the mean value for the control (non-SIDS NBW) group was significantly reduced (p < 0.01) from those of previous studies. This indicates that glomerular number reduction is seen in SIDS NBW and non-SIDS NBW cases and is therefore directly associated with growth retardation rather than with SIDS.

Birth Weight↗
PubMedDate not supplied

No influence of an aldose reductase inhibitor on glycogen deposition in tubules from streptozotocin diabetic rats.

Streptozotocin diabetic rats were divided into two groups. One diabetic group was given an aldose reductase inhibitor (Statil) throughout the study and the other group was left untreated. An additional group of nondiabetic rats was included in the study. After 7 months, the kidneys were perfusion fixed and blocks of tissue were sampled systematically and uniformly throughout the kidney cortex. Plastic embedded blocks were sectioned and used to determine the volume fraction of tubular glycogen by light microscopy. No difference was found between the two diabetic groups in glycogen deposits in the cortical thick ascending limb of Henle's loop, expressed as volume fraction per cortex. Tubules from control animals contained no visible glycogen, as opposed to a content of about 1% in both diabetic groups. We concluded that an aldose reductase inhibitor does not aggravate this tubular lesion (i.e., the Armanni-Ebstein lesion) in rats with experimental diabetes.

Aldehyde Reductase↗
PubMed1986

Presence of an extramitochondrial anion-stimulated ATPase in the rabbit kidney: localization along the nephron and effect of corticosteroids.

To determine whether kidney membrane fractions contain an extramitochondrial anion-stimulated ATPase, we compared the pharmacological and kinetic properties of HCO3-ATPase activities in mitochondrial and microsomal fractions prepared from rabbit kidney cortex and outer medulla. The results indicated that this activity differed markedly in each type of fraction. Microsomal HCO3-ATPase was less sensitive than mitochondrial ATPase to azide, oligomycin, DCCD and thiocyanate, but was more sensitive to filipin and displayed different dependency towards ATP, magnesium and pH. Microsomal ATPase activity was stimulated by sulfite much more strongly than by bicarbonate, whereas mitochondrial activity was stimulated by both these anions to a similar extent. These results demonstrate the presence of an extramitochondrial HCO3-ATPase in kidney membrane fractions. HCO3-ATPase was also measured in single microdissected segments of the rabbit nephron using a radiochemical microassay previously developed for tubular Na, K-ATPase activity. An enzyme with the pharmacological and kinetic properties of the microsomal enzyme was detected in both proximal tubule, distal convoluted tubule and collecting duct, but the thick ascending limb was devoid of any detectable activity. Long-term DOCA administration markedly increased HCO3-ATPase activity in the distal convoluted and collecting tubule. The insensitivity of microsomal HCO3-ATPase to vanadate indicates that it belongs to the F0-F1 class of ATPases, and might therefore be involved in proton transport. This hypothesis is also supported by the localization of tubular HCO3-ATPase activity at the sites of urinary acidification.

Adenosine Triphosphatases↗