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PubMed1977

Prolyl 3-hydroxylase: partial characterization of the enzyme from rat kidney cortex.

The formation of 3-hydroxyproline was studied with crude rat kidney cortex extract as a source of enzyme and chick embryo tendon protocollagen and procollagen or cartilage protocollagen as a substrate. Synthesis of 3-hydroxyproline was observed with all these substrates and the formation of 3-hydroxyproline ranged up to seven residues per pro-alpha-chain. The highest rate of 3-hydroxylation took place at 20 degrees C and the reaction required Fe2+, O2,2-oxoglutarate and ascorbate. The formation of 3-hydroxyproline was affected by chain length and the conformation of the substrate, in that longer polypeptide chains proved better substrates, while the native triple-helical conformation of protocollagen or procollagen completely prevented the reaction. Formation of 3-hydroxyproline with tendon procollagen as a substrate was not inhibited by antiserum to prolyl 4-hydroxylase or by poly(L-proline) when these substances were used in concentrations which clearly inhibited 4-hydroxyproline formation with tendon protocollagen as a substrate. Furthermore, pure prolyl 4-hydroxylase did not synthesize any 3-hydroxyproline under conditions in which the crude rat kidney cortex enzyme would readily do so. The data thus strongly suggest that prolyl 3-hydroxylase and prolyl 4-hydroxylase are separate enzymes.

Animals↗

PubMed1975

On the stimulation of gluconeogenesis by L-lysine in isolated rat kidney cortex tubules.

UNLABELLED: 1. L-Lysins (2 mM) stimulates (30-50%) gluconeogenesis in isolated kidney cortex tubules from 24-h-starved rats in the presence of lactate and Krebs cycle intermediates, but not pyruvate and glutamate. The stimulation of renal gluconeogenesis by L-lysine is a short-term effect. The effect is of catalytic nature, but not due to sparing of substrate. L-lysine caused a decrease of lactate/pyruvate ratio. 2. Apart from L-lysine, 1-10 mM NH-4Cl (16-40%) and 2 mM aspartate (66%) were capable to stimulate gluconeogenesis from lactate. Other amino acids tested did not stimulate renal gluconeogenesis, except L-alanine. The stimulation of gluconeogenesis by lysine was not additive to the stimulation by NH-4Cl. Likewise, there was no stimulation of gluconeogenesis from lactate by L-lysine in the presence of glutamate or arnithine. Levels of ammonia, glutamate and aspartate were elevated in the presence of L-lysine, NH-4Cl or glutamate about two-fold, were capable to stimulate gluconeogenesis. 3. The stimulation of gluconeogenesis by L-lysine from malate, succinate and oxoglutarate was abolished in the presence of amino oxy-acetate (0.05 mM), whereas controls were not significantly affected. 4. After 1 h of incubation about 5% of added [U-14C] lysine was recovered as 14-CO-2. The extra ammonia formed in the presence of L-lysine would also correspond with about 5-10% of added lysine being metabolized. 5. 14-CO-2 formation from [1-14C] butyrate and [1-14C] palmitate was inhibited by 20-30% in the presence of 2 mM L-lysine. 6. O-2 uptake and cellular levels of K+ were not significantly affected by L-lysine. 14-CO-2 fixation from pyruvate and 14-CO-2 formation from [1-14C]-pyruvate by isolated, intact rat liver mitochondria remained unchanged by L-lysine. Likewise no direct effect of L-lysine on enzyme activities could be detected. 7. CONCLUSION: The data seem compatible with the assumption that stimulation of gluconeogenesis in isolated kidney cortex tubules by L-lysine is due to a stimulation of the malate-aspartate shuttle as a consequence of an increased provision of glutamate and aspartate.

Amino Acids↗

PubMedDate not supplied

[Effect of starvation and diabetes on the activity of glucose-6-phosphate and 6-phosphogluconate dehydrogenases and on the free fatty acid content of rat kidney cortex and medulla].

Activity of dehydrogenases related to pentosephosphate pathway was not distinctly altered in soluble fraction of kidney cortex and medulla after 48 and 72 hrs of starvation. In diabetes the activity of these enzymes in rat kidney, as distinct from liver tissue, was not decreased but it was elevated and within 72 hrs after administration of alloxan the activity of glucose-6-phosphate dehydrogenase was increased 2-fold and the activity of 6-phosphogluconate dehydrogenase was increased by 30% above the normal level. Content of free fatty acids was also increased in kidney cortex of diabetic rats within 72 hrs after administration of alloxan. Alterations in content of free fatty acids were not observed either in kidney of diabetic animals within other studied periods (6 and 14-16 days) of treatment or in the tissue of starved rats. The data obtained suggest that free fatty acids do not participate immediately in controlling effect on dehydrogenases of pentosephosphate pathway in kidney in vivo.

Animals↗

PubMed1986

Carnitine metabolism in isolated rat kidney cortex tubules.

Renal carnitine metabolism was studied in isolated kidney cortex tubules from fed rats. The tubular distribution of free carnitine (C), acid-soluble short chain acylcarnitine (AcC), and total acid-soluble carnitine was measured. The content of the last-mentioned in rat cortical tubule suspensions was 2.85 +/- 0.15 nmol/mg protein, 46% representing AcC. In the absence of metabolic substrates the AcC/C ratio declined from 0.84 to 0.48 during incubation. The administration of 2mM acetoacetate or 2mM 3-hydroxybutyrate caused an increase in AcC by 45% and 51%, respectively. The rise in AcC was paralleled by a decrease in C, resulting in an increase of the tubular AcC/C ratio to 1.69 and 1.85, respectively. In the presence of 1 mM exogenous L-carnitine 35 +/- 6 nmol AcC/(mg protein X h) was formed. The addition of acetoacetate and 3-hydroxybutyrate led to a 3.5 to 3.8-fold rise in AcC formation. Other substrates which are likewise metabolized by proximal tubules were less effective. More than 90% of the formed AcC was recovered in the extracellular fluid. The results suggest that proximal renal tubule cells are the intrarenal site of carnitine acylation and may be involved in the regulation of blood and/or urinary carnitine acylation state.

3-Hydroxybutyric Acid↗

PubMed1989

Characterization of two possible forms of type IV collagen from human kidney cortex.

Type IV collagen was isolated from human kidney cortex according to the purification of mouse kidney type IV collagen (MKIVC) with minor modifications as described previously [Oikawa, T., et al. (1986) Chem. Pharm. Bull. 34, 789-797]. Chromatography of human kidney type IV collagen (HKIVC) on a column of DEAE-cellulose resulted in its separation into two fractions, i.e., one (HKIVC-1) passed through and the other (HKIVC-2) adsorbed to the column, similar to MKIVC. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Bio-Gel A-5m chromatography revealed that both HKIVC-1 and -2 differed from each other in the ratios of major and minor components. Amino acid analyses also demonstrated that there was a significant difference in the contents of several amino acid residues between both type IV collagens and their 80-kDa components, one of the major ones. These results indicate the possibility that there exist two forms of type IV collagen in human kidney.

Amino Acids↗

PubMed2003

Common single nucleotide polymorphisms of the MDR1 gene have no influence on its mRNA expression level of normal kidney cortex and renal cell carcinoma in Japanese nephrectomized patients.

In this study, we have quantified the mRNA expression levels of multidrug resistance gene 1 (MDR1) in the normal kidney cortex and renal cell carcinoma (RCC) segments from 24 Japanese nephrectomized patients by real-time polymerase chain reaction (PCR). The mRNA expression level of MDR1 in RCC segments was significantly decreased in comparison with each normal segment (P=0.0042, by Student's paired t-test). In addition, the ten common single nucleotide polymorphisms (SNPs) of the MDR1 gene in the patients were assessed using the PCR-restriction enzyme fragment length polymorphism method to investigate the influence of these SNPs on its mRNA expression levels. The allele frequencies of these SNPs were comparable with our previous report in the Japanese recipients of living-donor liver transplantation (Goto et al., Pharmacogenetics 12:451-457; 2002). MDR1 expression levels in the normal kidney cortex were independent on the five SNPs, which were polymorphic in the Japanese population. Furthermore, the effect of the SNPs on expression levels of MDR1 mRNA in RCC segments was not recognized. These findings suggest that the common SNPs in the MDR1 gene have no influence on the expression of its transcript in RCC segments as well as in the normal kidney cortex.

Adult↗

PubMed1990

Preferential distribution of streptomycin in pig kidney cortex.

In 14 pig kidneys containing streptomycin, an average distribution ratio of 2.5:1 was found for the streptomycin between the cortex and medulla. It is suggested here that cortex alone be used, instead of mixed kidney tissue, in regulatory meat monitoring schemes.

Animals↗

PubMed1992

A comparative study of the effects of cadmium on microsomal mixed-function oxidase activities between kidney cortex and liver.

The effects of cadmium and phenobarbital (PB) administration on the activities of microsomal mixed-function oxidase (MFO) in rat kidney cortex and liver were studied. Five indices, including cytochrome P-450 contents, aniline hydroxylase, NADPH-cytochrome c reductase, aminopyrine N-demethylase and 7-ethoxycoumarin O-deethylase activities, were assayed. By comparison, it was found that PB could induce MFO activities in kidney cortex microsomes and liver microsomes, both hepatic and renal microsomal MFO were decreased by the ip injection of CdCl2, and Cd2+ could markedly decrease the phenobarbital induction to hepatic and renal microsomal MFO activities with the exception of NADPH-cytochrome c reductase in kidney cortex microsomes.

Animals↗

PubMed1975

Isolation of peroxisomes from the dog kidney cortex.

The present study was undertaken to separate peroxisomes of the dog kidney cortex by the methods of discontinuous sucrose density gradient and zonal centrifugation. The separation of subcellular particles was evaluated by measuring the activities of reference enzymes, beta-glycerophosphatase for lysosomes, succinate dehydrogenase for mitochondria, glucose-6-phosphatase for microsomes, and catalase and D-amino acid oxidase for peroxisomes. The activities of D-amino acid oxidase and catalase were mainly observed in fractions 1 and 2 (1.6 and 1.7 M sucrose) obtained by discontinuous sucrose density-gradient centrifugation. Small amounts of acid phosphatase and succinate dehydrogenase contaminated these fractions. Considerably higher activity of catalase was determined in the supernatant, while D-amino acid oxidase showed a lower activity. By the method of zonal centrifugation, the highest specific activities of catalase and D-amino acid oxidase were found in fraction 50 (1.73 M sucrose) with no succinate dehydrogenase, acid phosphatase or glucose-6-phosphatase activity. These results suggested that peroxisomes of dog kidney cortex were clearly separated in 1.73 M sucrose from mitochondria, lysosomes and microsomes by zonal centrifugation.

Animals↗

PubMed1998

Mitochondrial aldehyde reductase: identification and characterization in rat liver and kidney cortex.

Aldehyde reductase (EC 1.1.1.2) has been regarded so far as an exclusively cytosolic enzyme. The present investigation shows that mitochondria of rat liver, kidney cortex and, tentatively, heart also contain an enzyme catalyzing oxidation of NADPH by aldehydes, p-nitrobenzaldehyde, methylglyoxal and glyceraldehyde. Activity of the mitochondrial enzyme can only be measured after the organelles are disrupted by sonication or solubilized with nonionic detergents. Mitochondrial aldehyde reductase activity contributed to about 4.6% and 2.5% of the total cellular activity in liver and kidney cortex, respectively. However, the specific activity in liver mitochondria was about one third and in kidney cortex mitochondria one tenth of that in the cytosol of the corresponding organ. The mitochondrial enzyme resembled the cytosolic one by its absolute specificity towards NADPH as the electron donor, a similar profile of aldehydic electron acceptors and identical Km values. Mitochondrial aldehyde reductase differed from the cytosolic enzyme by low sensitivity to known inhibitors of cytosolic aldehyde reductase, AL-1576, AL-4114 and ONO-2235. In liver, about 60% of the mitochondrial activity was tightly bound to the membranes whereas about 40% was present in the mitochondrial matrix. The membrane-bound activity was inactivated by digestion of mitoplasts with trypsin, alpha-chymotrypsin or papain, thus pointing to exposition of the substrate-binding site at the external surface of the inner membrane. On the other hand, latency of the enzyme in intact mitochondria indicates that the NADPH-binding site is located at the inner surface. These data provide the first direct evidence for the existence of aldehyde reductase in mitochondria of some rat tissues.

Aldehyde Reductase↗

PubMed1999

Altered expression and activity of G-proteins, mitogen activated protein kinases, and tyrosine kinases in aging kidney cortex.

BACKGROUND: Renal function declines with age and this may be related to changes in the expression or activity of various signal transduction proteins in the kidney. METHODS: The present study compared the expression and activity of G alpha i(1-3) and G alpha s phosphorylation of mitogen activated protein kinases (MAP-K) (44 and 42 kd) and the activity of tyrosine kinase in renal cortical homogenates of young (4-month-old) and aging (14-month-old) rats. RESULTS: The GTP/(GTP + GDP) binding ratio of G alpha s was significantly decreased in the kidney cortex of aging rats compared to young rats, while the GTP/(GTP + GDP) binding ratio of G alpha i(1-3) increased significantly in kidney cortex of aging rats. Tyrosine kinase activity and phosphorylation of MAP-K (44 and 42 kd) were also reduced in the kidney cortex of aging rats compared to young rats. CONCLUSIONS: These results suggest that diminished phosphorylation of MAP-K and tyrosine kinase activity as well as changes in the binding of GTP/(GTP + GDP) to G alpha i(1-3) and G alpha s may contribute to the age-related decline in renal tubular and vascular function seen in aging animals.

Aging↗

PubMed1988

Effect of fasting on lysosomes in kidney cortex of glomerulonephritic rats.

The effect of food restriction (FR) on the kidney cortex lysosomes prepared by rate and isopycnic zonal centrifugation was studied in rats with passive Heymann glomerulonephritis (PHN). FR reduced the renal mass by 41%, but the capacity for handling of labelled endocytosed proteins by the lysosomes was not different from fed PHN rats. While PHN with heavy proteinuria increased the recovery of lysosomal enzymes in the large lysosomes located in the proximal tubule, no changes were observed in FR-PHN rats in spite of significant proteinuria. The density of the small lysosomes was significantly shifted/reduced (from 1,200 and 1,235 g/ml to 1,185 and 1,225 g/ml, respectively) in both fed and FR-PHN rats, suggesting that the handling of extra loads of protein may enhance the absorptive function of small lysosomes found in the lower part of the nephron. FR reduced the mechanical fragility of lysosomes in the kidney cortex of PHN-rats. The highly increased urinary excretion of lysosomal enzymes in fed PHN rats was not observed in FR-PHN rats. As a conclusion, FR reduces both the fragility of lysosomes and the proportion of digestive enzymes in fragile lysosomes. These lysosomal enzymes may be of pathogenic importance in PHN causing cell damage when liberated from disrupted lysosomes.

Animals↗

PubMed1985

[Specific binding of organic acids by a fraction of the basolateral membrane of the rat kidney cortex isolated by osmotic shock].

Non-vesiculated membrane fragments of the basolateral membrane of the rat kidney cortex were isolated by the osmotic shock method and fractionated by means of differentional centrifugation. Formation and purity of membrane fragments were tested morphologically (contact luminescent, phase-contrast and electron microscopy) and biochemically (determination of the activity of marker enzymes--Na+, K+-dependent ATPase and alkaline phosphatase). The activities of Na+, K+-ATPase and alkaline phosphatase in the purified fraction of the basolateral membrane were 21 and 0.2%, respectively, of those in the kidney cortex homogenate. The binding of 14C-hyppuric and 14C-uric acids with basolateral membrane fragments was studied by means of filtration through the millipore filters. The existence of competitive inhibition and substrate saturation of the binding testify to the presence of organic acid carrier in the basolateral membrane. The affinity of the carrier to hyppurate in membrane preparations was proved to be the same as in the intact proximal tubules (the apparent Michaelis constant is equal to 0.7 mM). The equilibrium constant (Kf) for the carrier-hyppurate complex does not exceed 10 M-1. That means that the complex of the carrier with hyppurate is not strong.

Alkaline Phosphatase↗

PubMed1997

Activatory effect of calcium-binding protein regucalcin on ATP-dependent calcium transport in the basolateral membranes of rat kidney cortex.

The effect of regucalcin, a calcium-binding protein, on ATP-dependent Ca2+ transport in the basolateral membranes isolated from rat kidney cortex was investigated. The prepared membranes were in inside-out oriented and membrane vesicles. Ca(2+)-ATPase activity in the basolateral membranes was progressively elevated by increasing concentrations of regucalcin (10(-8) to 10(-6) M) in the reaction mixture. This increase was dependent on Ca2+ addition. The activatory effect of regucalcin on the enzyme is inhibited by the presence of digitonin (5 x 10(-3)%) which can solubilize the membranous lipids. Moreover, the regucalcin effect was clearly abolished by the presence of vanadate (0.1 mM) or N-ethylmaleimide (5.0 mM). However, the effect of calmodulin (6 x 10(-7) M) to increase Ca(2+)-ATPase activity was not significantly inhibited by vanadate or N-ethylmaleimide, indicating that the action mode of regucalcin differs from that of calmodulin. Also, the activatory effect of regucalcin on Ca(2+)-ATPase was appreciably inhibited by addition of dibutyryl cAMP (10(-5) and 10(-3) M), while inositol 1,4,5-trisphosphate (10(-7) and 10(-5) M) had no effect. Dibutyryl cAMP itself did not have an effect on the enzyme activity. Furthermore, the 45Ca2+ uptake by the basolateral membranes was clearly increased by the presence of regucalcin (10(-7) and 10(-6) M). This increase was completely blocked by the presence of vanadate (0.1 mM), N-ethylmaleimide (5.0 mM) or dibutyryl cAMP (10(-4) and 10(-3) M) in the reaction mixture. These results clearly demonstrate that regucalcin, which is expressed in rat kidney cortex, can increase Ca(2+)-ATPase activity and Ca2+ uptake in the basolateral membranes. Regucalcin may play a cell physiologic role as an activator in the ATP-dependent Ca2+ pumps in the basolateral membranes from rat kidney cortex.

Adenosine Triphosphatases↗

PubMed1997

Alterations in Ca2+-ATPase activity and calcium-binding protein regucalcin mRNA expression in the kidney cortex of rats with saline ingestion.

The alteration in calcium metabolism in rats ingested with saline was investigated. Rats were freely given saline as drinking water for 2 and 7 days. Calcium concentration in the serum was significantly elevated by saline ingestion for 2 and 7 days, while serum inorganic phosphorus concentration was not altered. Serum urea nitrogen concentration was significantly increased by saline ingestion for 7 days. Calcium content in the femoral-diaphyseal and metaphyseal tissues was not altered by saline ingestion for 7 days. Calcium content in the kidney cortex was significantly elevated by saline ingestion for 7 days. Ca2+-ATPase activity in the basolsateral membranes of kidney cortex was clearly increased by saline ingestion for 2 and 7 days. The enzyme activity was not altered by the addition of sodium chloride (10(-3) and 10(-2) M), parathyroid hormone (10(-7) and 10(-6) M), and calcitonin (3 x 10(-8) and 3 x 10(-7) M) in the enzyme reaction mixture. A calcium-binding protein regucalcin mRNA expression in the kidney cortex was markedly suppressed by saline ingestion for 7 days, although such a suppression was not seen for 2 days. These results suggest that saline ingestion causes the disturbance of calcium transport system in the kidney cortex of rats, and that the renal disorder may induce hypercalcemia.

Animals↗

PubMed1980

Different handling of parathyrin by basal-lateral and brush-border membranes of the bovine kidney cortex.

The two parts of the bovine kidney cortex plasma membrane, the basal-lateral and the brush-border membrane, were simultaneously prepared from the same organ. Both types of membrane bound parathyrin, but only from the basal-lateral fraction was the hormone displaceable by its bioactive N-terminal fragment. In parallel, parathyrin-stimulated adenylate cyclase was predominantly found in basal-lateral membranes. The hormone was fragmented by both membrane types. Basal-lateral membranes generated fragments with a rather uniform size distribution (somewhat smaller than the intact peptide) and apparently preferred the hormone itself as a substrate. In contrast, the fragments produced by brush-border membranes were numberous small peptides.

Adenylyl Cyclases↗

PubMed1986

Purification of lysosomal phospholipase A and demonstration of proteins that inhibit phospholipase A in a lysosomal fraction from rat kidney cortex.

Phospholipase A has been isolated from a crude lysosomal fraction from rat kidney cortex and purified 7600-fold with a recovery of 9.8% of the starting activity. The purified enzyme is a glycoprotein having an isoelectric point of pH 5.4 and an apparent molecular weight of 30,000 by high-pressure liquid chromatography gel permeation. Naturally occurring inhibitors of lysosomal phospholipase A are present in two of the lysosomal-soluble protein fractions obtained in the purification. They inhibit hydrolysis of 1,2-di[1-14C]oleoylphosphatidylcholine by purified phospholipase A1 with IC50 values of 7-11 micrograms. The inhibition is abolished by preincubation with trypsin at 37 degrees C, but preincubation with trypsin at 4 degrees C has no effect, providing evidence that the inhibitors are proteins. The results suggest that the activity of lysosomal phospholipase A may be regulated in part by inhibitory proteins. Lysosomal phospholipase A from rat kidney hydrolyzes the sn-1 acyl group of phosphatidylcholine, does not require divalent cations for full activity, and is not inhibited by ethylenediaminetetraacetic acid. It has an acid pH optimum of 3.6-3.8. Neither p-bromophenacyl bromide, diisopropyl fluorophosphate, nor mercuric ion inhibits phospholipase A1. In contrast to rat liver, which has two major isoenzymes of acid phospholipase A1, kidney cortex has only one isoenzyme of lysosomal phospholipase A1.

Animals↗

PubMed1971

Comparative analysis of the concentration of injected horseradish peroxidase in cytoplasmic granules of the kidney cortex, in the blood, urine, and liver.

The concentration of horseradish peroxidase in total particulate fractions from the kidney cortex did not change much during the first few hours after injection, as long as most of the injected protein was not yet cleared from the blood. It decreased at a rate of 6-8% per hr afterwards. The concentration of peroxidase in total particulate fractions increased in proportion to the load (dose) over a wide range, suggesting that a constant fraction of the protein was reabsorbed by micropinocytic vesicles into the tubule cells from the glomerular filtrate. The amount of peroxidase excreted in the urine also increased in proportion to the injected dose. The proportion of peroxidase taken up by the liver, however, decreased several times when the dose was increased. A marked decrease of protein uptake into the kidney cortex and an increase of urinary excretion were observed when rats received a second, equal dose of peroxidase 4 hr after the first injection, and the rate of clearance of peroxidase from the blood was decreased after the second injection. The liver, on the other hand, took up almost twice as much peroxidase after two injections as after one. The uptake of peroxidase by the kidney cortex increased with age. Cytochemical observations on the preferential absorption of peroxidase by certain cell types and segments of the renal tubules in relation to dose are reported.

Absorption↗