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PubMed1986

Secretion control for active and inactive renin: effect of ouabain on release from rabbit kidney cortex slices.

Release of active and inactive renin by rabbit kidney cortex slices was investigated. Inactive renin was estimated as the increase in renin activity after acidification (pH 2.8) of slice supernatant solutions. For kidney slices incubated in complete Krebs bicarbonate buffer, the Na-K-ATPase inhibitor ouabain (100 microM) reduced the secretion of both active (-19.2%) and inactive (-78.9%) forms of renin. In low Na buffers ([Na+] = 23 mM) active renin release was increased and inactive renin was suppressed. Both of these changes were abolished by addition of ouabain (100 microM). The reduction in inactive renin secretion produced by ouabain in complete Krebs buffer did not occur in low [Na+] buffers. In zero Ca2+ buffers containing EGTA (5 mM), secretion of both active and inactive renin was increased but these changes were abolished by addition of ouabain (100 microM). Incubating kidney slices in low Na+, zero Ca2+ media revealed differences between the secretion control mechanisms for the two forms of renin. The separate stimulatory effects of low Na+ and low Ca2+ were not additive for the release of active renin and inclusion of ouabain resulted in similar secretion rates to those under control conditions. For inactive renin secretion, in the absence of Ca2+ release mechanisms still respond to reduction in Na+ with decreased secretion. Conversely, in low Na+ buffers, removal of Ca2+ still promotes inactive renin secretion. These changes were abolished by the addition of ouabain (100 microM). Slices did not change in weight during incubation in media which did not contain ouabain. Addition of this inhibitor to control buffers and low Na buffers did result in an increase in weight. This correlated with the presence of Ca2+ in the buffer and did not appear to be related to [Na+]. These studies again show that the mechanisms regulating the secretion of active and inactive renin are not identical and support the hypothesis that Na+ have differing roles to play in the regulation of these two forms of renin.

Animals↗

PubMed1990

Effects of hyper- and hypothyroidism on carbonic anhydrase, Mg2(+)-dependent ATPase and Mg2(+)-dependent, HCO3(-)-stimulated ATPase activities of rat duodenal mucosa and kidney cortex.

Carbonic anhydrase (CA) and Mg2(+)-dependent ATPase and Mg2(+)-dependent, HCO3(-)-stimulated ATPase (Mg2(+)-HCO3(-)-ATPase) activities in rat duodenal mucosa and kidney cortex were examined with respect to thyroidal status. Administration of 50 and 150 micrograms thyroxine (T4)/kg per day s.c. for 7 days decreased duodenal cytosol CA activity to 66% of control with the former and 43% with the latter dose, while Mg2(+)-HCO3(-)-ATPase activity in brush borders of duodenal mucosa was increased to 116% of control by 150 micrograms T4/kg. CA and Mg2(+)-HCO3(-)-ATPase activities in the cytosol and brush border of kidney cortex did not change after administration of T4. Hypothyroidism induced by thyroidectomy for 2 and 4 weeks or administration of methimazole (2.5-20 mg/kg per day s.c. or peroral) for 2, 3 and 4 weeks all increased duodenal cytosol CA activity, to about 140% at 2 weeks and 153% at 4 weeks after thyroidectomy, and to about 136% after the oral administration of 10 mg methimazole/kg per day for 4 weeks, while brush border Mg2(+)-HCO3(-)-ATPase activity was decreased to 56% of control 4 weeks after thyroidectomy and to 74% after the s.c. administration of 20 mg methimazole/kg day for 3 weeks. The increase in CA activity and the decrease in ATPase activity after thyroidectomy were restored to normal levels by replacement with T4. Neither enzyme activity in the kidney changed in hypothyroidism. Serum concentrations of T4 and cortisol-like material increased after administration of T4, and serum concentrations of T4, aldosterone and cortisol-like material all decreased in hypothyroidism. Correlations were observed between duodenal CA and Mg2(+)-HCO3(-)-ATPase activities and serum concentrations of T4 (P less than 0.01). These results reveal that the decrease in CA activity and the increase in Mg2(+)-HCO3(-)-ATPase activity of duodenal mucosa in hyperthyroidism are reversed in hypothyroidism, while both enzyme activities in the kidney are unrelated to thyroidal status.

Adenosine Triphosphatases↗

PubMed1977

A phosphodiesterase in rat kidney cortex that hydrolyses glycerylphosphorylinositol.

1. A phosphodiesterase, active at an alkaline pH, is present in the outer cortex of rat kidney and hydrolyses glycerylphosphorylinositol into glycerol and phosphorylinositol. Some inositol cyclic phosphate can also be formed indicating that the enzyme can act as a cyclizing phosphotransferase. 2. The enzyme is stimulated by Ca2+(2-3mM) whereas Mg2+ is inhibitory. 3. The activity is markedly stimulated by low concentrations of thiol reagents (1-2mM) such as cysteine or dithiothreitol. 4. The properties of the enzyme have been compared with glycerylphosphinicocholine diesterase (EC 3.1.4.2), which is also present in the isolated enzyme complex, and it is concluded that the enzymes have separate identities.

Animals↗

PubMed1982

Inhibition of ischemic induced cellular swelling in kidney cortex tissue by lactobionate anions.

Tissue slices prepared from the cortex of canine kidneys exposed to various periods of normothermic ischemia rapidly and massively swell when placed in oxygenated Ringer's lactate medium. The swelling can be suppressed by replacing part of the chloride with larger, less permeable anions such as lactobionate. By adjusting the ratio of lactobionate:Cl- to 60 mM:80 mM respectively, periods of greater than 90 min of ischemia can be tolerated without cell swelling. The lactobionate:Cl- medium is effective at preventing cell swelling at osmolalities approaching isoosmolar conditions. A fluid containing the appropriate levels of lactobionate and Cl- may be beneficial in the resuscitation of ischemic or shocked exposed organ systems by suppressing reflow-related cell swelling.

Animals↗

PubMed1985

Glutamic acid decarboxylase in tubules and glomeruli isolated from rat kidney cortex.

4-Aminobutyric acid (GABA) synthesis was examined in purified glomeruli and tubules of rat kidney cortex that were incubated in the presence of [2,3-3H2]glutamate. The GABA that was formed was separated from glutamate using anion-exchange resin, and identified by means of an automatic amino acid analyser. In the renal cortex only the tubules were able to form GABA (35.0 nmol mg-1 h-1); the remaining GABA synthesis found in the glomerular preparations can most probably be attributed to a contamination by cortical tubules (9%), as shown by determination of a known tubular marker enzyme (L-gamma-glutamyltransferase). Hydroxylamine (1 mM) and ethanolamine-O-sulfate (10 mM), well-known inhibitors of cerebral GABA formation and GABA catabolism respectively, inhibited renal tubular GABA formation at 100% and 44% respectively.

Animals↗

PubMed1983

[Topochemistry of aminopeptidase A (angiotensinase A) in the kidney cortex of the golden hamster].

The localization of aminopeptidase A (APA; E.C. 3.4.11.7) in the kidney cortex of the golden hamster was demonstrated by histochemical means (simultaneous azo coupling technique; alpha-L-Glu-MNA as substrate and HNF as coupling agent). APA was shown in the renal corpuscle (mainly podocytes and epithelium of the Bowman's capsule), the brush border of the proximal tubule, the perivascular tissue and some peritubular capillaries.--The demonstration of APA in the perivascular tissue of the juxtaglomerular apparatus (JGA) appears to have bearing on the regulation of angiotensin effects in the JGA for APA is an angiotensin degrading enzyme.

Aminopeptidases↗

PubMed1991

Human renin activation by protease from the renin granule fraction of the dog kidney cortex.

To clarify the possible conversion of prorenin in renin granules where conversion reportedly occurred, we investigated whether the renin granule fraction of the kidney could activate prorenin to the active form. Renin granules were isolated from the dog kidney cortex by discontinuous sucrose density gradient centrifugation. Human active renin was quantified by immunoradiometric assay which could detect only the human active renin but not the inactive human renin or dog renin. Inactive renin from human amniotic fluid was incubated with the subcellular fraction of the dog kidney cortex. The renin granule fraction that showed the highest renin activity stimulated the inactive renin to become the active form. The membrane preparation obtained from the renin granule fraction by freezing and thawing the fraction in low osmolarity retained the activity of renin activation. Other subcellular fractions showed less renin activation. The optimal pH for renin activation by the membrane was pH 5.0 to 6.0. The activation depended on the time of incubation and concentration. The activation was inhibited by N-ethylmaleimide but not by EDTA or serine protease inhibitors. These results suggest that renin is processed by a membrane bound protease in renin granules.

Amniotic Fluid↗

PubMed2006

Purification and kinetics of sheep kidney cortex glucose-6-phosphate dehydrogenase.

Glucose-6-phosphate dehydrogenase (G-6-PD) is one of the important enzymes, which is responsible for the production of NADPH and ribose-5-phosphate. NADPH is used for the biosynthetic reactions and protection of the cells from free radicals. We have investigated some properties and kinetic mechanism of the sheep kidney cortex G-6-PD. This enzyme has been purified 1,384-fold with a yield of 16.96% and had a specific activity of 27.69 U/mg protein. The purification procedure consists of 2', 5'-ADP-Sepharose 4B affinity chromatography after ultracentrifugation. The sheep kidney cortex G-6-PD was found to operate according to a Ping Pong Bi Bi mechanism. The kinetic parameters from sheep K(m) values for G-6-P and NADP(+) and V(m) were determined to be 0.041+/-0.0043 mM, 0.0147+/-0.001 mM and 28.23+/-0.86 microMol min(-1) mg protein(-1), respectively. The pH optimum was 7.4 and the optimum temperature was 45 degrees C. In our previous study we have found that lamb kidney cortex G-6-PD enzyme obeys 'Ordered Bi Bi' mechanism. We suggest that kinetic mechanism altered due to the aging since sheep G-6-PD uses a 'ping pong' mechanism.

Aging↗

PubMed1992

The effects of arachidonic acid and its CoA ester on the catabolism of prostaglandin E2 in rabbit kidney cortex.

The effects of arachidonic acid and arachidonoyl CoA on the catabolism of prostaglandin E2 in a 105000 x g supernatant fraction from rabbit kidney cortex were examined. Arachidonic acid reduced the 15-hydroxy prostaglandin dehydrogenase activity by 50% at 20 microM, while arachidonoyl CoA showed weak inhibition for the enzyme activity (15% at 20 microM). However, arachidonoyl CoA strongly inhibited the prostaglandin delta 13 reductase activity, the concentration required for 50% inhibition being about 3 microM. The dehydrogenase inhibition by arachidonic acid was non-competitive with regard to NAD+ and prostaglandin E2, respectively. Arachidonoyl CoA was also a non-competitive inhibitor for the reductase with regard to NADH and 15-keto prostaglandin E2, respectively. These results suggest that arachidonic acid and arachidonoyl CoA can be important modulating factors in prostaglandin catabolism by the kidney cortex.

15-Oxoprostaglandin 13-Reductase↗

PubMed1979

Divalent cation transport in kidney slices. I. Properties of calcium transport in slices of rat kidney cortex and the effects of diuretics.

Correlative studies on transports of Ca2+ and Na+ and the properties of Ca2+ transport were carried out in rat kidney cortex slices. Ouabain had no effect on the Ca2+ transport but did inhibit the Na+ transport extensively. With addition of 2,4-dinitrophenol to the incubation medium, or under the anaerobic conditions, the effluxes of Ca2+ and Na+ were inhibited while the Ca2+ influx was enhanced significantly. Sulfhydryl inhibitors such as ethacrynic acid, mersalyl and p-chloromercuribenzoic acid suppressed Ca2+ efflux and stimulated Ca2+ influx. When the slices of kidney cortex were treated with these inhibitors, there was a reduction in the content of cellular ATP. The present results suggest that Ca2+ transport may be partly independent of Na+ transport, and that Ca2+ efflux may require energy-yielding processes.

Adenosine Triphosphate↗

PubMed1976

Transport of p-aminohippuric acid by plasma membrane vesicles isolated from rat kidney cortex.

Basal-lateral plasma membrane vesicles and brush border membrane vesicles were isolated from rat kidney cortex and the uptake of p-aminohippuric acid (PAH) into these vesicles was studied by Millipore filtration techniques. Both membrane preparations take up PAH into an osmotically reactive intravesicular space. The transport across the brush border membrane seems to involve only simple diffusion whereas in the basal-lateral plasma membrane in addition a specific transport system exists which is inhibited competitively by probenecid. The apparent affinity of this transport system for PAH is 5.4 X 10(-4) M and for probenecid 5.4 X 10(-5) M. PAH uptake into basal-lateral plasma membrane vesicles is influenced by alteration of the membrane potential. Maneuvers which render the intravesicular space more positive--as for example replacement of chloride by sulfate in the presence of a sodium gradient directed into the vesicles and addition of valinomycin in the presence of a potassium gradient directed into the vesicles--stimulate the uptake of PAH. Replacement of a sodium chloride gradient by a sodium thiocyanate gradient reduces the uptake probably by reducing the inside positive membrane potential. In the absence of salt gradients anion replacement and replacement of sodium by potassium does not affect PAH transport by basal-lateral plasma membranes. These results suggest that in isolated basal-lateral membranes transfer of PAH across the membrane is accompanied by a transfer of negative charge. They furthermore provide no evidence for the existence of a sodium-PAH cotransport system in this membrane preparation.

Aminohippuric Acids↗

PubMed1986

Lack of effect of short-term treatment with high doses of gentamicin on the level and subcellular distribution of cholesterol in rat kidney cortex.

Treatment of rats with 100 mg gentamicin sulfate/kg body weight by intraperitoneal injection once or twice daily for 3 days had no effect on the level of cholesterol in the kidney cortex, indicating that gentamicin does not affect the metabolism of this lipid under these conditions. Nor did such treatment cause any major subcellular redistribution of cholesterol in the kidney cortex, i.e., processes such as intracellular membrane traffic did not seem to be disturbed.

Animals↗

PubMedDate not supplied

[Characteristics of cysteine peptidohydrolases from the human kidney cortex].

Spectrum of cysteine peptide hydrolases was studied in human kidney cortex using a variety of protein and synthetic substrates after the preparation was fractionated on Sephadex G-100 following the precipitation with ammonium sulfate 40-70%. Activities of dipeptidyl aminopeptidase I, lysosomal carboxypeptidases A and B, cathepsins B and H, as well as the activity of Ca+2-dependent neutral proteinase were detected. A thiol-dependent proteolytic activity, which was apparently stimulated by cathepsin T- and -M like enzymes, was also observed. Besides, the proteinase with molecular mass of 50-60 KDa and high hemoglobin and casein splitting activity was found. This activity cannot be attributed to any of the proteinases so far known. Isoelectrofocusing technique showed that two forms of cathepsin B occurred in human kidney with isoelectric points at pH 5.32 and pH 5.65; two forms of cathepsin H were also detected exhibiting isoelectric points at pH 6.03 and pH 6.7.

Chromatography, Gel↗

PubMed1975

Stimulation of cellular autophagy by parathyroid hormone and cyclic adenosine 3',5': monophosphate in isolated tubular fragments from the rat's kidney cortex.

Tubular fragments isolated from the cortex of the rat's kidney were qualitatively and quantitatively investigated with the electron microscope. The tubules frequently burst open and became "inverted" in such a way that the rarefied brush border now formed the outer circumference. By morphometry a decrease of the average cell volume in the proximal tubular fragments was ascertained. This was mostly caused by a loss of cytoplasmic ground substance, endoplasmic reticulum and ribosomes. Cytoplasmic herniations of the basal surface, filled with free ribosomes, suggested a partial shedding of the protein synthesizing apparatus. The number of autophagic vacuoles (AV) per unit area of cytoplasm was determined in proximal tubular fragments. After isolation alone, without further incubation, the number of AV was as low as the number found in an earlier study in proximal tubular cells in situ during the diurnal minimum. After control incubation the number of AV increased to about the mean value of the AV found in cells in situ during the whole diurnal cycle. By comparison with the control incubation the number of AV increased by a factor of 1.6 to 1.7, if cyclic adenosine 3',5': monophosphate (cyclic AMP) or parathyroid hormone (PTH) were added to the incubation-medium; it now reached about the number of AV found in situ during the diurnal maximum. The increase in the number of AV paralleled that of the production of ammonia and glucose from endogenous sources under the influence of cyclic AMP and PTH. This suggests that the breakdown of cytoplasmic components by cellular autophagy could be functionally related to gluconeogenesis. A quantitative comparison between the measured production of ammonia and glucose indicates, however, that in the system of isolated tubular fragments there may exist other mechanisms of degradation, and of the provision of substrates for gluconeogenesis, than cellular autophagy only.

Animals↗

PubMed1981

Polarized Zeeman-effect flameless atomic absorption spectrometry of cadmium, copper, lead, and manganese in human kidney cortex.

We used polarized Zeeman-effect flameless atomic absorption spectroscopy to quantitatively measure cadmium, copper, lead, and manganese in a nitric acid digest of lyophilized human kidney cortex. Within-run coefficients of variation for cadmium, copper, lead, and manganese, 15.3, 177.2, 84.2, and 56.3 microgram/L, respectively, were 4.1, 6.3, 3.7, and 5.6%, respectively. Between-run coefficients of variation were 6.9, 5.5, 5.9, and 6.3%, respectively, for cadmium, copper, lead, and manganese concentrations of 135.1, 12.8, 2.72, and 3.80 microgram/g, respectively. For cadmium, copper, lead, and manganese digest concentrations (mean +/- SE) of 15.3 +/- 0.6, 41.4 +/- 2.6, 9.4 +/- 0.6, and 20.9 +/- 0.4 microgram/L, respectively, the detection limits were 5.2 microgram/L for copper, 1.2 microgram/L for both cadmium and lead, and 0.8 microgram/L for manganese. Assays were linear to 75 microgram/L for cadmium, 100 microgram/L for manganese, and 200 microgram/L for copper and lead. Average analytical recoveries for the four metals ranged between 95 and 101%. Because these metals were quantitated in the same digest of kidney cortex, the values for each digest gave a trace-metal profile for each autopsy specimen.

Cadmium↗

PubMed1986

The lysosomal distribution of cathepsin B in the rat kidney cortex.

Subcellular distribution of cathepsin B following subfractionation of the kidney cortex mitochondrial/lysosomal fraction by rate sedimentation indicates that this enzyme is mainly associated with the large, fast sedimenting lysosomes (protein droplets). A small proportion of cathepsin B is also present in the small lysosomes which cosediment with mitochondria, peroxisomes, and brush border and other large membrane vesicles. Amongst this broad spectrum of small lysosomes the distribution of cathepsin B, together with other acid hydrolases is associated with the more rapidly sedimenting lysosomes whilst cathepsin D differs in being associated with the slowest sedimenting lysosomes. Equilibrium banding in sucrose gradients shows the large lysosomes band at a density of 1.235 g/ml and that the small lysosomes have two distinct populations at densities 1.20 and 1.235 g/ml. Cathepsin B (and also cathepsin D and acid ribonuclease) appears to be associated only with lysosomes of high density. The various other acid hydrolases assayed are found in all the lysosomal populations. Small and large lysosomes of high density are very rich in a number of proteinases and therefore most probably represent lysosomal populations involved in the catabolism of proteins taken up from the glomerular filtrate.

Animals↗

PubMed1978

Effects of ethacrynic acid on ion transport and energy metabolism in slices of avian salt gland and of mammalian liver and kidney cortex.

Ethacrynic acid greatly inhibited net transport of ions and aerobic, energy-conserving metabolism in slices of avian salt gland, rat liver, and rat and guinea-pig kidney cortex. The effects of increasing concentrations of ethacrynic acid on the transport of Na+, K+ and Cl- ran closely parallel to its effects on tissue ATP levels and respiration. The concentration needed for maximal inhibition of transport reduced ATP levels by 80--90%. Respiration was reduced by 80--90% in salt gland and kidney cortex, and by a maximum of 30% in liver slices. The effects of low concentrations of ethacrynic acid required time to become fully manifest in some tissues, and the development of transport inhibition followed a similar course to decline of respiration and ATP levels. Ca2+ extrusion by liver cells was inhibited by ethacrynic acid. The concentration dependence of the inhibition was similar to that shown by the other transport systems inhibited. There was no distinction evident between the sensitivity of Na+ extrusion and of K+ accumulation to the diuretic. Lactate production increased as respiration decreased in the presence of increasing concentrations of ethacrynic acid. We conclude that ethacrynic acid acted primarily as an inhibitor of mitochondrial respiration and ATP synthesis in the tissue slices, and that inhibition of ion transport was a nonspecific consequence of the failure of the energy supply.

Adenine Nucleotides↗

PubMed1986

Effect of age and diabetes on type IV collagen and laminin in human kidney cortex.

Specific radioimmunoassays for the 7-S domain of type IV collagen and the fragment P1 of laminin were used to quantify these basement membrane proteins in human kidney cortex at different ages and in some patients with diabetes mellitus. The antigens were solubilized by treating the tissue samples with the proteolytic enzymes collagenase, trypsin and pepsin. Total collagen content (as indicated by hydroxyproline concentration) increased with age, and the proportion of the collagen that could be solubilized by any enzyme treatment decreased. The type IV collagen concentration increased significantly with age, whereas the laminin concentration tended to decrease. In the one case of a type I diabetic the amounts of both antigens exceeded those in the age matched controls. In four type II diabetics the results were comparable with those for other aged cases. The distribution of the proteins was studied using the peroxidase-antiperoxidase method. The staining intensity and thickness of both antigens increased with age in the mesangium and Bowmans capsules, the change in type IV collagen staining being more evident. In diabetic patients these changes were more pronounced and other basement membranes appeared thicker in the stainings. These results indicate that basement membrane material accumulates in the kidney cortex during aging and that an alteration takes place in the composition of the basement membranes, the proportion of type IV collagen increasing and that of laminin decreasing.

Adolescent↗