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PubMed1986

Isolation and characterization of peroxisomes from the renal cortex of beef, sheep, and cat.

The isolation and characterization of highly purified and structurally well-preserved peroxisomes from the renal cortex of different mammalian species (beef, sheep, and cat) is reported. Renal cortex tissue was homogenized and a peroxisome-enriched light mitochondrial fraction was prepared by differential centrifugation. This was subfractionated by density-dependent banding on a linear gradient of metrizamide (1.12-1.26 g/cm3) using a Beckman VTi 50 vertical rotor. Peroxisomes banded at a mean density of 1.225 cm3. Ultrastructural morphometric examination revealed that peroxisomes made up 97 to 98% of the isolated fractions. By biochemical analysis the contamination with marker enzymes of mitochondria and lysosomes was extremely low. The specific activity of catalase was enriched, depending on the species, between 28- and 38-fold over the homogenate. Peroxisome preparations from all three species exhibited a high but varying level of activity for cyanide-insensitive lipid beta-oxidation. In beef and sheep preparations a small amount of esterase activity cosediments with peroxisomes. These peroxisomes show distinct structural membrane associations with smooth elements of ER. Urate oxidase, a marker enzyme for rat liver peroxisomes, is found only in peroxisomes prepared from beef kidney cortex, with sheep and cat preparations being negative. This correlated with the occurrence of polytubular inclusions in the beef kidney peroxisomes. The large size and the angular shape of isolated peroxisomes as well as the presence of paracrystalline matrical inclusions imply that the majority of peroxisomes are derived from the epithelial cells of the proximal tubule of the kidney cortex. The significant differences found in the characteristics of the renal peroxisomes in three different species investigated, demonstrate the remarkable adaptability and plasticity of this organelle.

Animals↗
PubMed1983

Polarised X-rays in XRF-analysis for improved in vivo detectability of cadmium in man.

A technique is described for the in vivo XRF-analysis of cadmium in the kidney cortex of man using plane polarised photons for excitation. The polarised photons are produced by scattering the radiation from an X-ray tube (W anode, 150 kV, 15 mA) in a polymethylmethacrylate disc at a 90 deg angle. The beam paths (X-ray tube to scatterer, scatterer to sample, sample to detector) must represent three mutually orthogonal directions. The minimum detectable concentration for a counting time of 1800 s and a skin-kidney distance of 30 mm is 8 micrograms g-1. This is a factor of 2.5 lower than our earlier method with direct excitation using the 59.5 keV photons from 241Am. The energy imparted has also been lowered from 0.4 to 0.2 mJ. The cadmium concentration in the kidney cortex of six occupationally exposed persons varied between 15 and 170 micrograms g-1.

Cadmium↗
PubMedDate not supplied

[Effect of insulin and hydrocortisone on the isoenzyme composition of pyruvate kinase in the rabbit kidney].

Alloxan diabetes, starvation of rabbits within one day and administration of hydrocortisone during 5 days did not cause distinct alterations in the total activity of pyruvate kinase in kidney cortex. At the same time pronounced alterations in the isozyme spectra were observed: the L-type activity of pyruvate kinase was decreased and the M2-type of activity was increased. The total activity and the isozyme content of pyruvate kinase were only slightly altered in starvation of rabbits during 3 or 10-16 days and after administration of protamine-Zn-insulin during 3 days. Hydrocortisone caused variable effects on the pyruvate kinase isozymes from kidney cortex, depending on periods of administration.

Animals↗
PubMed1975

The activities and intracellular distribution of nicotinamide-adenine dinucleotide phosphate-malate dehydrogenase, phosphoenolpyruvate carboxykinase and pyruvate carboxylase in rat, guinea-pig and rabbit tissues.

1. Measurements are presented of the activity and intracellular distribution of phosphoenolypruvate carboxykinase, pyruvate carboxylase and NADP-malate dehydrogenase in rat, guinea-pig and rabbit liver and kidney cortex, together with previously obtained measurements of these enzymes in adipose tissue. 2. In all three tissues pyruvate carboxylase activity was greatest in the rat and lowest in the rabbit. 3. Guinea pig and rabbit were very similar to each other with respect to the extramitochondrial-mitochondrial distribution of phosphoenolpyruvate carboxykinase in all three tissues. 4. NADP-malate dehydrogenase was present in all three tissues in the rat, present in kidney cortex and adipose tissue in the guinea pig and absent from all tissues examines in the rabbit.

Adipose Tissue↗
PubMed2000

Comparative studies on Na-dependent Pi transport in ovine, caprine and porcine renal cortex.

In contrast to monogastric species, renal excretion of inorganic phosphate (Pi) in ruminants is low and this could be attributed to an almost complete tubular Pi reabsorption. However, the functional and regulatory basis for this phenomenon has not yet been clarified. Therefore, it was the aim of the present study to characterize the kinetic parameters of the tubular Pi reabsorption system as affected by P or Ca depletion using preparations of renal cortex brush border membrane vesicles (BBMV) from goats and sheep and to compare the data with respective parameters of porcine preparations. Na-dependent Pi uptake into renal cortex BBMV as a function of Pi concentration showed typical Michaelis-Menten kinetic and respective Scatchard plot analysis of the specific Pi uptake revealed linearity indicating the predominant presence of a single type of Pi transporters in the preparations. Under control conditions Vmax values of Na-dependent Pi uptake into BBMV were highest in goats and sheep and lowest in pigs (1.98, 1.39 and 0.95 nmol x mg(-1) protein x 10s(-1), respectively). Km values were not different between goats and sheep under all feeding conditions and ranged from between 0.34 mmol x l(-1) and 0.55 mmol x l(-1) which was three- to five-times higher than that found in pigs (0.11 mmol x l(-1)). Oligonucleotides derived from rat kidney cortex type IIa Na/Pi cDNA were used for reverse transcriptase-polymerase chain reaction (RT-PCR) in goat, sheep and pig kidney cortex. The products isolated were 768 bp for sheep and pigs and 765 bp for goats, with the respective amino acids sequences, representing a segment of approximately 40% in length of the entire transporter, exhibiting an at least 92% sequence homology between different species. From the results, involvement of type IIa Na/Pi cotransport in tubular Pi reabsorption in small ruminants can be postulated. However, it should not be considered that a potential role of other Pi transport systems be completely be excluded. Interestingly, neither P nor Ca depletion caused significant effects on Na-dependent Pi transport capacities and affinities in goats and sheep. From this, parathyroid-hormone independent regulatory pathways of tubular Pi reabsorption can be assumed.

Animals↗
PubMed1977

The development of pyruvate dehydrogenase in the subhuman primate Macaca mulatta.

The development of total pyruvate dehydrogenase activity in the subhuman primate, Macaca mulatta, was investigated in brain, liver, kidney cortex, and skeletal and cardiac muscle. Newborn primates delivered prematurely at 135 days of gestation had only 32% of this enzyme activity present in the brain compared to the full-term animal. Full-term animals were similar to adults. All tissues showed high activities of enzyme at 1 year of age compared either with neonates or adults. Kidney cortex showed an increase in activity from 807 +/- 74 mumol/g/min in prematurely delivered neonates to a maximum of 3,769 +/- 275 mumol/g/min in 1-year-old animals. The results are discussed in relation to the developing energy requirements of the tissues concerned.

Age Factors↗
PubMed1982

Cortical cell populations from rabbit kidney isolated by free-flow electrophoresis: characterization by measurement of hormone-sensitive adenylate cyclase.

Free-flow electrophoresis allows the separation of different cell populations from a cell suspension isolated from rabbit kidney cortex after perfusion of the kidneys with a calcium-binder, followed by gentle mechanical treatment. After electrophoretic separation, analysis of the adenylate cyclase activities after stimulation by various hormones allows the precise determination of the origin of the cell populations with different electrophoretic mobilities. Adenylate cyclase from the slow-moving main cell population was only sensitive to parathyroid hormone. These cells had also high alkaline phosphatase content, further demonstrating their proximal origin. The various fast-moving cell populations had adenylate cyclase sensitive to isoproterenol and arginine vasopressin but were less sensitive to parathyroid hormone than the slow-moving cells. Their alkaline phosphatase content was also much lower. This indicates that these fast-moving cell populations originate from both the granulous segment of the distal tubule and from the collecting ducts. The adenylate cyclase activity and the cyclic AMP contents of isolated proximal cells maintained in culture medium were also investigated.

Adenylyl Cyclases↗
PubMed1976

Regulation of phosphoenolpyruvate carboxykinase by glutamine and ATP as possible control mechanisms of renal gluconeogenesis.

In different metabolic states renal phosphoenolpyruvate carboxykinase (PEP-CK) activities are closely correlated with in vitro glucogenic rates, suggesting a limitation of the glucogenic capacity of kidney by this enzyme. Stimulation of renal gluconeogenesis from pyruvate, lactate, and succinate by lysine and glutamine was therefore associated with a regulatory attack of these amino acids at the level of PEP-carboxykinase. This postulate was confirmed by the failure of lysine to stimulate glucose synthesis from fructose. Experimental support for an interference of glutamine and PEP-carboxykinase was obtained by a study on the inactivation of this enzyme in kidney cortex homogenates: A rapid inactivation of enzyme activity within 40-50 min could be slowed down by glutamine. In addition the inactivation was counteracted by ATP. At suboptimal concentrations of the trinucleotide its effect was potentiated by c-AMP and c-GMP. Studies on the effect of ATP on PEP-carboxykinase in kidney cortex homogenates from rats in different metabolic states revealed: In homogenates from carbohydrate fed animals extreme low activities of PEP-CK were not altered by ATP, whereas elevated enzyme activities after a protein rich diet could be further raised by a factor of 2 or 3 by ATP. GTP and ITP could substitute for ATP. An extension of these studies on hepatic enzymes showed a similar inactivation of tyrosine aminotransferase (TAT) and a protective effect of ATP. The data obtained from these experiments favour an interconversion of PEP-carboxykinase and tyrosine aminotransferase into different forms as possible mechanism for their regulation.

Adenosine Triphosphate↗
PubMed1989

Tissue distribution of radiolabelled human factor D in the male Sprague-Dawley rat.

Human factor D was purified, labelled with 125I and injected intracardially or intraperitoneally into male Sprague-Dawley rats. After intracardial administration, 80% of the radioactivity seen initially in the blood was eliminated within 5 min. The highest levels of radioactivity were recovered in the kidney cortex in both cases: maximally 24% of the total dose applied was recovered in this tissue 7 min after intracardial injection and 8-9% of the total dose 80-90 min after intraperitoneal administration. Significant amounts of radioactivity were also observed in the spleen, lungs, liver and heart muscle, but uptake by other tissues was very low. These results indicated that injected human factor D disappeared rapidly from the plasma of rats and uptake by the kidney cortex was one of the main routes of elimination.

Animals↗
PubMed1978

Renal gluconeogenesis in clofibrate-treated rats.

Clofibrate was administered in the diet (0.3% w/w) for varying periods of time to normal rats. Rats were killed by decapitation and several biochemical measurements were made. Clofibrate lowered serum levels of cholesterol and triglyceride and produced a kidney hypertrophy; these effects were maximal after 3 days of feeding and persisted for 21 days. Serum clofibric acid levels were highest on the 3rd day and decreased to maintenance levels by the 7th day. Clofibrate markedly increased the activities of glucose 6-phosphatase, pyruvate carboxylase and phosphoenolpyruvate carboxykinase in kidney cortex and the synthesis of glucose from glutamate, lactate, pyruvate, glycerol and malate by kidney cortex slices. Clofibrate treatment did not affect blood pH or bicarbonate levels. It is concluded that clofibrate enhances renal gluconeogenesis in the rat and that the effect is not caused by altering acid-base balance.

Animals↗
PubMed1975

Distribution of renin in subcellular fractions from the rabbit kidney.

Subcellular localization of renin in the rabbit kidney cortex was investigated using two centrifugation techniques. Renin was indirectly assayed on the basis of pressor activity and the reference enzymes such as succinic dehydrogenase, acid phosphatase and D-glucose-6-phosphatase for the other subcellular particulates were biochemically determined. Renin activity was found mainly in the mitochondrial fraction with very little in the microsomal fraction by a differential centrifugation. By a discontinuous sucrose density gradient centrifugation, renin granules were mainly recovered in the fraction corresponding to 1.5 M sucrose, while most of mitochondria, lysosomes and microsome equilibrated in the upper fractions. This renin granular fraction contained approximately 50% of total granular renin activity having a specific activity about six times that seen in the homogenate. After recentrifugation of the renin granular fraction, most of renin activity was recovered in the sediment. Repeated freezing and thawing of this fraction resulted in an increase of renin activity. On the basis of these experimental data it is assumed that renin located in the different subcellular particulates from mitochondria, lysosomes and microsomes in the rabbit kidney cortex.

Angiotensin II↗
PubMed1982

Insulin prevention of impaired renal calcium transport in alloxan-diabetic rats.

The uptake of calcium-45 was measured in slices of kidney cortex from rats with alloxan-diabetes of increasing durations. Slices from untreated diabetic rats had significantly lower slice-to-medium ratios for calcium than did slices from control rats, reflecting decreased uptake of calcium by cortical slices from diabetic rats. Institution of daily insulin therapy immediately upon confirmation of diabetes prevented this depression of calcium uptake, even though the insulin therapy was insufficient to control blood glucose levels. After four weeks of untreated alloxan-diabetes, insulin therapy did not return calcium uptake by kidney cortex slices to control levels.

Animals↗
PubMed1989

Production and characterization of monoclonal antibodies against particulate guanylate cyclase in porcine kidney.

Three monoclonal antibodies (Ig G1 type) to particulate guanylate cyclase from porcine kidney cortex have been produced by fusing spleen cells from immunized BALB/c mouse with P3X63 myeloma cells. The antibodies were detected by their ability to bind immobilized antigen and by immunoprecipitation of enzyme activity. After subcloning by limiting dilution, hybridomas were injected intraperitoneally into mice to produce ascitic fluid. The antibodies recognized a 180,000 dalton protein in Lubrol-PX extract of porcine kidney cortex membrane, and when immobilized on Sepharose 4B, they co-precipitated both [125I]human atrial natriuretic peptide (ANP)-receptor complex and guanylate cyclase activity. The antibodies caused a greater increase in generation of cGMP than that of ANP.

Animals↗
PubMed1975

Distribution of anticancer agents in spontaneous animal tumors. II. Distribution of gallium in canine lymphosarcoma.

The physiologic disposition of pharmacologic doses of gallium was studied in control dogs and dogs with spontaneous lymphosarcoma. Gallium 67 (67Ga) was administered iv with carrier gallium added at a dose of 8 mg/kg. About 50% of the injected dose was excreted in the urine by 48 hours (mostly in the first 12 hr), whereas negligible amounts were excreted in bile. The distribution of 67Ga in normal tissues was similar in control and tumor-bearing dogs. The tissue-to-plasma concentrations of gallium were considerably greater than 1 in the kidney cortex, bone marrow, bone, small intestine, and liver 6-72 hours after administration of the drug. At comparable time periods, tissue-to-plasma ratios of gallium were less than 1 in skeletal muscle and brain. In dogs with lymphosarcoma there was neither selective uptake nor selective retention of gallium in comparison to most normal tissues. In fact, several normal tissues, particularly kidney cortex and bone marrow, concentrated gallium greatly in excess of tumors. Qualitatively similar findings were obtained in a dog with malignant melanoma. These findings were contrary to what one would predict from reports showing that carrier-free 67Ga is selectively concentrated in various human and animal tumors. This indicates the need for more extensive studies of the physiologic disposition of pharmacologic (antitumor) doses of gallium in humans and appropriate animal models.

Animals↗
PubMed2003

Increased endothelin-1 expression in the kidney in hypercalcemic rats.

BACKGROUND: Although hypercalcemia causes diuresis and natriuresis, the molecular mechanisms of these effects are not well established. Recently, the important role of the calcium-sensing receptor (CaR) in hypercalcemia-induced polyuria was reported. Endothelin-1 (ET-1) that is locally produced in the nephron has been suggested to have the natriuretic and/or diuretic effects in the kidney. Therefore, we hypothesized that ET-1 expression could be increased through the activation of CaR in the kidney in hypercalcemia. METHODS: Rats were made hypercalcemic by dihydrotachysterol (DHT) treatment. The urinary concentration of ET-1 and the mRNA expression of ET-1 in the kidney were determined. Immunohistochemistry was performed to determine types of the cells that produce ET-1. CaR and ET-1 promoter luciferase constructs were co-expressed in COS-7 cells and the ET-1 promoter activity following the addition of extracellular calcium was measured by the luciferase assay. RESULTS: In hypercalcemic rat, urinary ET-1 excretion was increased by twofold, and ET-1 mRNA expression was increased in the kidney cortex by threefold. In cortical collecting duct (CCD), both principal cells and intercalated cells synthesized ET-1. In cells that express CaR, ET-1 promoter was activated in a dose-dependent manner by extracellular calcium over the range of 0.5 to 3.0 mmol/L. CONCLUSIONS: First, activation of CaR increases ET-1 transcription in a dose-dependent manner. Second, hypercalcemia increases ET-1 production in the kidney cortex. These data suggest the possibility that CaR might play an important role in hypercalcemia-induced increase in ET-1 production.

Animals↗
PubMed1992

Guanine nucleotides stimulate carboxyl methylation of kidney cytosolic proteins.

We studied the effect of guanine nucleotides on the carboxyl methylation catalyzed by class II protein carboxylmethyltransferases (PCMT). Addition of guanosine 5'-O-(gamma-thio)triphosphate (GTP gamma S) promoted a time- and concentration-dependent enhancement of protein methylation in the cytosolic fraction isolated from kidney cortex. GTP gamma S affected the kinetics of the methylation reaction, as reflected by alterations of both apparent Km and Vmax of the methyltransferase. This effect was specific for guanine nucleotides and was completely abolished by addition of S-adenosyl-L-homocysteine, a well-known inhibitor of methyltransferase-catalyzed reactions. No GTP gamma S stimulation of methylation was found in cytosolic extracts from any of the other tissues studied, including brain, testis, spleen, and liver, nor in brush-border membranes isolated from the kidney cortex. The methylated proteins were highly sensitive to moderately alkaline conditions, suggesting that the methyl esters were formed on L-isoaspartyl residues and thus methylated by a class II PCMT. These results suggest that class-II-associated protein methylation activity from the soluble fraction of the kidney can be regulated by guanine nucleotides.

Animals↗
PubMed1983

The effect of cigarette smoke on aryl-hydrocarbon hydroxylase (AHH) activity of the human kidney.

AHH activity was measured in kidney cortex biopsies obtained during surgery from patients with hydronephrosis and from unaffected portions of kidneys with renal cell carcinomas. AHH activity was slightly, but not significantly, higher in the group of non-smoking cancer patients when compared to non-smoking hydronephrotic subjects. Smoking induced a significant increase of AHH activity in the hydronephrotic kidneys but not in cancer kidneys, probably due to the higher baseline values and scatter in the cancer group. Pooling cancer and non-cancer kidneys, smokers had a higher AHH activity than non-smokers, this increase being dose-related.

Adenocarcinoma↗
PubMed1990

[Characterization of surface fluorescence signals of isolated perfused rat kidney].

The NAD(P)H- and flavoprotein fluorescence signals of the isolated perfused rat kidney were characterized by their electrochemical properties and by comparing them with those of isolated kidney cortex mitochondria. From titration experiments with lactate pyruvate under anoxic conditions it is concluded that about 25% of the NAD(P)H-fluorescence can be attributed to the cytosolic pyridine nucleotides. For this signal a midpoint potential of -268 mV was calculated. The major part of the NAD(P)H-fluorescence signal was of mitochondrial origin, showing a midpoint potential of -304 mV which was titrated with beta-hydroxybutyrate/acetoacetate. A comparable value (Em7.4 = -310 mV) was found for isolated kidney cortex mitochondria using the same redox couple. The flavoprotein fluorescence could be totally attributed to the mitochondrial compartment and was found to originate from the NAD-dependent alpha-lipoamide dehydrogenase and the electron transfer flavoprotein of beta-oxidation to approx. 60% and 40%, respectively. A midpoint potential of -285 mV was determined for the NAD-dependent part of the flavoprotein signal. On the basis of these results it can be concluded that the fluorescence changes which were caused by ouabain in the normoxically perfused rat kidney reflect an increase in reduction of the mitochondrial NAD-system.

3-Hydroxybutyric Acid↗