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PubMed1988

[Effect of dopamine on the blood flow in various zones of the kidney cortex and medullary layer in rats].

Phentolamine and propranolol did not alter the kidney response to dopamine whereas haloperidol completely prevented the dopamine vascular and channel effects. The agents inhibiting cyclooxygenase and kallikrein-kinin system do not interfere with an increase in the blood flow or depressing action of the neurotransmitter upon sodium transport in the nephron. The hemodynamic shift occurring under the effect of dopamine in different areas of renal tissue seems to be due to a selective stimulation of vascular DA-receptors and unrelated to an increase in the production of prostaglandins and kinins in the kidneys.

Animals↗
PubMed1986

Purification and characterization of two forms of cytochrome P-450 from rat kidney cortex microsomes.

Two forms of cytochrome P-450 (P-450), designated P-450 k-1 and P-450 k-2, have been purified about 100-fold from rat kidney cortex microsomes. P-450 k-1 and P-450 k-2 have monomeric molecular weights of 51,500 and 52,000, respectively, on sodium dodecyl sulfate(SDS)-polyacrylamide gel electrophoresis. Absolute spectra of the oxidized forms indicate that P-450 k-1 is largely in the low-spin state and partly in the high-spin state, and that P-450 k-2 is essentially all in the former. The absorption maxima in reduced carbon monoxide difference spectra are at 450.5 and 451 nm with P-450 k-1 and P-450 k-2, respectively. The two P-450s catalyze the omega- and (omega-1)-hydroxylation of fatty acids such as caprate, laurate, myristate, and palmitate, although P-450 k-1 exhibits a higher specific activity with all fatty acids tested. In addition, P-450 k-1 is capable of hydroxylating prostaglandin (PG) A1 and A2 at the omega-position, whereas P-450 k-2 has no activity toward PGs. These activities are all stimulated by addition of cytochrome b5. The two P-450s give different peptide map patterns when partially digested with Staphylococcus aureus V8 protease or papain.

Animals↗
PubMed1979

Further evidence for the existence of an intrinsic bicarbonate-stimulated Mg2+-ATPase in brush border membranes isolated from rat kidney cortex.

The aim of this study was to provide further evidence for the existence of a nonmitochondrial becarbonate-stimulated Mg2+-ATPase in brush border membranes derived from rat kidney cortex. A plasma membrane fraction rich in brush border microvilli and a mitochondrial fraction were isolated by differential centrifugation. Both fractions contain a Mg2+-ATPase activity which can be stimulated by bicarbonate. The two Mg2+-ATPases are stimulated likewise by chloride, bicarbonate, and sulfite or inhibited by oligomycin and aurovertin, though to different degrees. In contrast to these similarities, only the Mg2+-ATPase activity of the mitochondrial fraction is inhibited by atractyloside, a substance which blocks an adenine nucleotide translocator in the inner mitochondrial membrane. On the other hand, filipin, an antibiotic that complexes with cholesterol in the membranes inhibits exclusively the Mg2+-ATPase of the cholesterol-rich brush border membranes. Furthermore it could be demonstrated by the use of bromotetramisole, an inhibitor of alkaline phosphatase activity, that the Mg2+-ATPase activity in the membrane fraction is not due to the presence of the highly active alkaline phosphatase in these membranes. These results support the assumption that an intrinsic bicarbonate-stimulated Mg2+-ATPase is present in rat kidney brush border membranes.

Adenosine Triphosphatases↗
PubMed1980

Effect of a proteinase inhibitor, aprotinin, on brush border membrane associated aminopeptidase of human kidney cortex.

In order to study the influence of the basic proteinase inhibitor aprotinin (Trasylol) on renal tubular alanine-aminopeptidase (E.C.3.6.11-), a brush border fraction was prepared from human kidney cortex by differential centrifugation. Incubation of brush border fragments, rich in membrane bound alanine-aminopeptidase, resulted in an activation of the enzyme. However, aminopeptidase, which was cleaved off from the membranes by limited proteolysis and subsequently purified by Concanavalin A-affinity chromatography exhibited activation by low but inhibition by higher concentration of aprotinin. Thus inhibition was associated with presence of the solubilized form of the brush border enzyme. On the other hand, as was shown by quantitative electroimmunoassay, formation of antigen-antibody complexes between soluble renal aminopeptidase and its specific rabbit antibody was not changed by the basic polypeptide.

Aminopeptidases↗
PubMed1992

Curative effect of methionine on certain enzymes of chick kidney cortex under lanthanum toxicity situation.

Acute single dose administration of lanthanum chloride (250 mg/kg body wt, ip) to chicks have been found to alter the levels of enzymes of the antioxidant defence system of chick renal cortex fractions. Such changes involved significant decrease in activities of glucose-6-phosphate dehydrogenase, glutathione reductase, glutathione peroxidase and catalase of kidney epithelial cells. However glutathione-S-transferase activity was not altered. Glutathione and total thiol contents were decreased while lipoperoxidative reactions in kidney-cortex was significantly enhanced. The data indicate that amelioration of lanthanum toxicity condition by methionine supplementation may be due to the methionine serving as a precursor of glutathione.

Animals↗
PubMed1986

Indirect immunoselection of late distal cell populations from rabbit kidney cortex.

This study describes a method for the separation of distal cell populations based on the sequestration of proximal cells on immunoadsorbent columns (CNBr-activated Sepharose 6MB) bound with three brush-border monoclonal antibodies (S6-Mab). A high yield of isolated cell suspension from rabbit kidney cortex was prepared by mechanical dissociation after perfusion and incubation of the kidneys with 10(-3) M EDTA. The sequestration of the proximal cells was achieved in two sequential chromatographic steps. About 92% of the applied cells were first retained on an S6-Mab column after a 60-min stationary stage and the unbound cells were submitted by direct flow to a second S6-Mab column. In such conditions, 8 X 10(6) cells were recovered when starting with 331 X 10(6) cortical cells. The efficiency of the proximal cell depletion process was confirmed by an 80% decrease in brush-border enzymes, a very low phosphoenolpyruvate carboxykinase activity, and absence of cells bearing long microvilli, as ascertained by electron microscopy. This immunodepleted cell population presented the enzymatical characteristics of cells from the more distal segments. As compared with the initial cell suspension, these cells exhibited higher hexokinase (2.3 times), succinate dehydrogenase (1.5 times), and Na+-K+-ATPase (2.6 times) activities. In addition, adenylate cyclase activities remained sensitive to parathormone, arginine vasopressin, and isoproterenol. The functional capacity of these immunodepleted cells was assessed by an almost complete exclusion of eosin dye, a low Na+ and high K+ intracellular content, and a high respiratory rate of oxygen consumption. In conclusion, this immunoselective process makes it possible to obtain subpopulations of renal cortical cells possessing the main characteristics of the distal, connecting, and collecting cells for physiological and metabolic studies.

Adsorption↗
PubMed1978

Glutamate metabolism in relation to glutamate transport in kidney cortex mitochondria of rabbit.

1. The metabolism of glutamate was followed by measurements of phosphoenolpyruvate production, aspartate synthesis and ammonia release, whereas the transport of glutamate across the inner membrane of kidney cortex mitochondria was studied using an oxygen electrode and the swelling technique. 2. When added separately, avenaciolide and aminooxyacetate only partially inhibited both State 3 and uncoupled respiration of the mitochondria, as studied in the presence of glutamate as substrate. In contrast, the addition of both inhibitors to the reaction medium resulted in an almost complete inhibition of glutamate oxidation. 3. Swelling of kidney mitochondria in an isosmotic solution of ammonium glutamate was accelerated by uncoupler and inhibited by avenaciolide, while the swelling of mitochondria in potassium glutamate was stimulated by valinomycin and inhibited by uncoupler. 4. When glutamate was used as the sole substrate, inhibition of aspartate formation by aminooxyacetate resulted in a stimulation of both ammonia release and phosphoenolpyruvate production. In contrast, with glutamate plus malate as substrate an elevation of the rate of glutamate deamination on the addition of aminooxyacetate was accompanied by an inhibition of phosphoenolpyruvate synthesis in both State 3 and uncoupled conditions. 5. In the presence of valinomycin to induce K+-permeability a marked enhancement of glutamate deamination was accompanied by a significant inhibition of glutamate transamination. 6. Based on the presented results it was concluded that in rabbit renal mitochondria utilizing glutamate as substrate the rate of ammonia production, phosphoenolpyruvate formation and aspartate synthesis vary in response to different metabolic conditions, in which both the glutamate--H+ symport and the glutamate--aspartate exchange systems are functioning to different extents.

Aminooxyacetic Acid↗
PubMed1983

Androgenic stimulation of endocytosis, amino acid and hexose transport in mouse kidney cortex involves increased calcium fluxes.

Testosterone was previously shown to induce an early (less than 1 min) receptor-dependent stimulation of endocytosis, hexose and amino acid transport in mouse kidney cortex (Koenig, H., Goldstone, A. and Lu, C.Y. (1982) Biochem. Biophys. Res. Commun. 104, 165-172). Testosterone (10(-8) M) has now been found to stimulate rapidly (less than 30 s) the influx and efflux of 45Ca2+ in cortex slices. Testosterone also decreased mitochondrial 45Ca and augmented soluble 45Ca, indicating a mobilization of intracellular calcium. Incubation of cortex slices in calcium-free medium without or with 2.5 mM EGTA decreased basal endocytosis, hexose and amino acid transport and blocked the hormonal response. 100 microM verapamil blocked the hormonal response without affecting basal transport. The calcium ionophore A23187 rapidly stimulated endocytosis, hexose and amino acid transport. These data indicate that androgenic stimulation of membrane transport functions involves an increased influx of extracellular calcium and a mobilization of intracellular calcium. Increased cytosolic Ca2+ is probably the regulatory signal for these transport processes.

Amino Acids↗
PubMed1983

Comparison of the effect of temperature on kidney cortex mitochondria from rabbit, dog, pig, and human: Arrhenius plots of ADP-stimulated respiration.

The effect of temperature on the rate of ADP-stimulated respiration of mitochondria from dog, rabbit, pig, and human kidney cortex mitochondria was plotted according to the Arrhenius relationship. The temperature at which the plot demonstrated a break was at 15 degrees C for mitochondria from dog, pig, and human kidneys. The discontinuity occurred at 10 degrees C or less for mitochondria from rabbit kidneys. This difference suggests that mitochondria from rabbit kidneys undergo a lipid-phase transition at lower temperatures than for other species commonly used in experimental renal preservation. The implications of this difference suggest caution in using results obtained with rabbit kidneys for comparison to results obtained from hypothermic renal preservation of other species kidneys. Apparent fluidization of dog kidney mitochondrial membranes with adamantine abolished the discontinuity in the Arrhenius plot.

Adamantane↗
PubMed1987

[Effect of the natriuretic factor on the transport of electrolytes and energy metabolism in kidney cortex sections].

The peptide material of the 2nd and 3rd fractions of the natriuretic factor did not affect the passive sodium transport while inhibiting the active transport in slices of the rat kidney cortex. This inhibition was accompanied by a decrease of both the succinic dehydrase system and Na+, K+-activated ATPase activities in the slices. The natriuresis caused by the natriuretic factor seems to be due to the inhibition of the active sodium transport.

Animals↗
PubMed1990

Intracellular distribution of gentamicin within the rat kidney cortex: a cell fractionation study.

The present study demonstrates that during the first 1.5-3 min after a single intraperitoneal administration of [3H]gentamicin to rats, most of the radioactivity in the kidney cortex is recovered in the cytosolic and microsomal fractions upon subcellular fractionation. Subsequently, the level of radioactivity recovered in the cytosolic fraction decreases markedly, whereas this level remains relatively unchanged in microsomes and increases somewhat in the nuclear and mitochondrial fractions. A steady state is apparently reached 13 hr after the injection. The high initial concentration of gentamicin in the cytosol may indicate that this substance is taken up to a large extent by diffusion. Such uptake is somewhat surprising, because of the polar nature of gentamicin. The small size of this drug may, however, allow it to diffuse through so-called pores and/or interaction with negatively charged phospholipids may be involved in the uptake of gentamicin. The initial total level of radioactivity recovered in microsomes after in vivo administration of [3H]gentamicin was considerably higher than in the nuclear and mitochondrial-lysosomal fractions. Furthermore, when gentamicin was added directly to kidney homogenate prepared from untreated rats, instead of being administered in vivo, this substance was still recovered in highest amounts in the total microsomal fraction. This observation may indicate that enrichment of gentamicin in the endoplasmic reticulum (or fragments thereof) reflects a special affinity of this drug for these membranes and is probably not the result of a particular in vivo process. There was no difference in the levels of radioactivity recovered in smooth and rough microsomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

Effect of urine metabolites from healthy and uremic subjects on gluconeogenesis in slices of rat kidney cortex and liver.

A high molecular weight fraction was obtained by extended dialysis of urine of healthy and uremic subjects. After addition to the incubation medium, this fraction inhibited gluconeogenesis by rat kidney cortex slices. From the six subfractions extracted by gel chromatography (Sephadex G 100) fraction IV caused a decrease of glucose formation. The activity of PEP-carboxykinase but not of pyruvate carboxylase was reduced, indicating a decreased formation of phosphoenol pyruvate. The total high molecular weight fraction stimulated glucose release by liver slices from fed but not from starved rats. In the absence of amino acids, urea formation was not stimulated. The activity of pyruvate carboxylase was reduced in both groups, PEP-carboxykinase activity was, however, only reduced in the starved group. The addition of uremic serum caused increased glucose release. Inhibition of PEP-carboxykinase activity by quinolinic acid (15 mM) resulted in inhibition of glucose formation by 35% in the uremic group and 54% in the control group in livers of 24 hr starved rats. Thus in uremia there may be incorporation of serine carbon skeletons into glucose via hydroxypyruvate, not via pyruvate. Chromatography on calibrated columns indicated that about 40% of the urinary fractions had molecular weights in the upper range of the "middle molecules" category. The positive correlation between toxicity and the total amount of high molecular weight substances excreted do not confirm the hypothesis of augmented retention of "toxins" in uremic patients. It must be appreciated that these results refer only to the undialyzable fraction of urine which contains only 0.5% by weight of the total urine solids.

Animals↗
PubMed1985

Photoaffinity labeling of atrial natriuretic factor receptors of rat kidney cortex plasma membranes.

Synthetic rat atrial natriuretic factor (ANF) was derivatized with the N-hydroxysuccinimide ester of [125I]iodoazidosalicylic acid to yield a radioactive photoaffinity probe. Incubation of purified plasma membranes from rat kidney cortex with this photoaffinity probe resulted in the specific labeling of a 140-kDa glycoprotein. The photoaffinity labeling of this protein was inhibited by ANF but not by reduced and alkylated ANF nor by other unrelated peptides. A 140-kDa band was also specifically labeled in liver plasma membranes but not in adipocyte plasma membranes. These observations suggest strongly that the 140-kDa glycoprotein is the ANF receptor.

Adipose Tissue↗
PubMed1976

[O2-consumption and CO2 formation by kidney cortex sections incubated in an optimal substrate mixture].

Basing on the knowledge of renal metabolism a substrate mixture has been developed which appears to be promising for the preservation of this organ. Slices of rat kidney were incubated in different solutions, and the oxygen consumption and 14CO2 formation were determined at 6 degrees C after 4 and 9 hrs. In the substrate mixture the rat kidney cortex shows a continual O2 consumption, which could be increased by more than twice the amount compared with the values obtained after incubation without substrate. The proportion of fatty acid and amino acid mixture supplied amounts to 90% of the total CO2 formation by the renal cortex. Under the conditions selected, the incubation mixture allows one to spare endogenic substrates. The criteria of O2 consumption and CO2 formation alone are not sufficient to decide whether the functioning of the mitochondria and thus the energy supply are ensured under these conditions. Further studies are necessary to solve this problem.

Amino Acids↗
PubMed1990

Purification and characterization of two forms of fatty acid omega-hydroxylase cytochrome P-450 from rabbit kidney cortex microsomes.

We have previously reported the isolation of two forms of cytochrome P-450 (P-450) with omega-hydroxylase activities toward prostaglandin A (PGA) and fatty acids, designated as P-450ka-1 and P-450ka-2, from kidney cortex microsomes of rabbits treated with di(2-ethylhexyl)phthalate [Kusunose, E. et al. (1989) J. Biochem. 106, 194-196]. In the present work, we have purified and characterized two additional forms of rabbit kidney fatty acid omega-hydroxylase, designated as P-450kc and P-450kd. The purified P-450kc and P-450kd had specific contents of 13 and 16 nmol of P-450/mg of protein, with apparent molecular weights of 52,000 and 55,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), respectively. Both the forms showed absorption maxima at 450 nm in the carbon monoxide-difference spectra for their reduced forms. These P-450s efficiently catalyzed the omega- and (omega-1)-hydroxylation of fatty acids such as caprate, laurate, myristate, and palmitate, in a reconstituted system containing P-450, NADPH-P-450 reductase, and phosphatidylcholine. Cytochrome b5 stimulated the reactions to only a slight extent. They had no detectable activity toward PGA and several xenobiotics tested. The two P-450s showed different peptide map patterns after limited proteolysis with papain or Staphylococcus aureus V8 protease.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1982

Rabbit kidney cortex phosphorylase phosphatases: evidence for complexes between high molecular weight forms and heat-stable inhibitor proteins.

Two forms of high molecular weight phosphorylase phosphatase have been partially resolved by gel filtration chromatography of rabbit kidney cortex extracts. Two heat-stable inhibitor proteins co-eluted with the phosphatase peaks. Phosphorylase phosphatase and heat-stable inhibitor activity also co-migrated on gel electrophoresis of cortex extracts. When extracts were heated to 95 degrees for 5 minutes prior to gel filtration or electrophoresis, phosphorylase phosphatase inhibitor activity eluted at a lower molecular weight and a higher mobility, respectively. Storing cortex extracts at -20 degrees for 6 months resulted in partial conversion of both phosphatase and inhibitor activities to lower molecular weight forms which co-eluted on gel filtration. The two inhibitor peaks from gel filtration chromatography were heat-treated and characterized. Both inhibitor peaks had molecular weight of 25,000 to 35,000. The inhibitory activity of one of the peaks was increased about 3.5-fold by incubation with cyclic AMP-dependent protein kinase and ATP, and required higher concentrations of TCA to be precipitated. Hence, one of the inhibitor peaks resembled rabbit muscle inhibitor -1, while the other peak may represent an inhibitor similar to rabbit muscle inhibitor -2. These results represent the first indication that low molecular weight heat-stable inhibitor proteins may be bound to high molecular weight phosphorylase phosphatases in the cell.

Animals↗
PubMed1990

Pertussis toxin attenuates angiotensin II but not beta-adrenoceptor facilitation of noradrenaline release from rat kidney cortex.

1. Angiotensin II (AII; 0.01 and 0.1 mumols/L), angiotensin I (AI, 0.1 mumols/L) and the beta-adrenoceptor agonist isoprenaline (0.1 mumols/L) all facilitated the stimulation-induced outflow of radioactivity from slices of rat kidney cortex incubated in [3H]-noradrenaline. 2. Treatment of rats with pertussis toxin (25 and 50 micrograms/kg i.v.) to inactivate G-proteins attenuated the facilitation caused by AII and AI, but not that caused by isoprenaline. 3. The hypothesis that isoprenaline enhances noradrenaline release by generating AII to activate facilitatory prejunctional AII receptors is not supported by the present study. The hypothesis predicts that pertussis toxin, by inactivating the G-proteins associated with AII receptors, should have inhibited the facilitatory effect of isoprenaline. This did not occur.

Angiotensin I↗