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Results for “Kidney Cortex”

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PubMed1989

Cisplatin-induced changes in cytochrome P-450, lipid peroxidation and drug-metabolizing enzyme activities in rat kidney cortex.

This study investigates the effects of 3 successive cisplatin administrations on rat kidney cytochrome P-450 and drug-metabolizing enzyme activities. Furthermore, because glutathione (GSH) and its related enzymatic system are involved in cellular detoxification processes, we examined the effects of cisplatin on lipid peroxidation, GSH levels, and GSH reductase and peroxidase activities. Cisplatin induced a decrease in cytochrome P-450, GSH, GSH S-transferase, GSH reductase and GSH peroxidase activities, and an increase in N-glucuronyl transferase, lipid peroxidation and oxidized glutathione (GSSG) in kidney cortical microsomes and cytosolic fractions. It is suggested that cisplatin nephrotoxicity could be explained by its affinity for SH-groups of several enzymes and SH-containing compounds. Among these, GSH and its related enzymatic system play a primary role. Moreover, cisplatin increases lipid peroxidation, which might participate in cisplatin nephrotoxicity.

Animals↗
PubMedDate not supplied

Proteomic analysis of rat kidney cortex following treatment with gentamicin.

The regionally specific structure and function of the kidney renders it susceptible to toxic exposure. To characterize these changes at the proteome level, we have investigated the effects on protein expression following treatment with gentamicin. The more than 20 proteins identified were involved in the citric acid cycle, gluconeogenesis, fatty acid synthesis, and transport or cellular stress responses. These results strongly support the notion that energy production is impaired and mitochondrial dysfunction is involved in gentamicin-induced nephrotoxicity.

Animals↗
PubMed2005

Gene profiling the effects of calcium deficiency versus 1,25-dihydroxyvitamin D induced hypercalcemia in rat kidney cortex.

Determinants involved in the activation and repression of 1,25-dihydroxyvitamin D (1,25(OH)(2)D(3)) synthesis in renal cortex by changes in extracellular Ca were studied. Cortical kidney RNA isolated from hypocalcemic (LC) rats generated by a low Ca diet, and hypercalcemic (HC) rats generated by a normal Ca diet and two sequential 1 microg doses of 1,25(OH)(2)D(3). Among the genes up-regulated were 1alpha-OHase (4.6-fold) in the LC group and high differential gene expression of VDR (4.0-fold) and 24-OHase (10.4-fold) in the HC group. Moreover, the exposure of renal cortex to LC versus HC conditions revealed a high differential expression of a PKA-dominated pathway involving CBP interacting protein, GATA-1 and CREB transcription factors in the LC model. In the HC model, elevated renal cortex gene expression of several growth factors, peptide receptors, and intracellular signaling molecules depicts a role for CaSR activation and receptor tyrosine kinase signaling in 1,25(OH)(2)D(3)-mediated gene activation and repression of 1alpha-OHase.

Animal Feed↗
PubMed1975

Cell electrical potentials during enhanced sodium extrusion in guinea-pig kidney cortex slices.

1. Experiments were performed on outermost slices of the guinea-pig kidney which are mainly made up of proximal tubular cells. 2. Kidney cells loaded with Na+ by chilling at 0.6 degrees C for 2.5 hr, when subsequently rewarmed to 25 degrees C in a medium containing 16 mM-K+ extrude Na+ at enhanced speed for about 10 min. This Na+ movement is accompanied by efflux of Cl and influx of K+. 3. Measurements of cell potential during enhanced Na+ extrusion show that cells hyperpolarize to values about 30 mV more negative than the K+ equilibrium potential. 4. This hyperpolarization is only partly inhibited by 1 mM ouabain or by 2 mM ethacrynic acid but both agents added together suppress it completely. 5. With 16 mM-Rb instead of 16 mM-K the hyperpolarization is smaller. 6. A diminished extracellular K+ concentration outside of the cells, within the slice, can account for only a small part of the hyperpolarization. 7. The hyperpolarization is proportional to the rate of Na+ pumping. 8. Cl- seems to shunt the hyperpolarization to a greater extent than K+. 9. It is concluded that Na+ extrusion is capable of transferring electric charge across the membrane.

Animals↗
PubMed1972

The effect of steroids and ammonium chloride acidosis on phosphoenolpyruvate carboxykinase in rat kidney cortex. II. The kinetics of enzyme induction.

The kinetics of the induction of rat kidney phosphoenolpyruvate carboxykinase activity after triamcinolone and ammonium chloride administration have been investigated with a view to the further differentiation of the two processes. The half-life of kidney phosphoenolpyruvate carboxykinase activity, as measured from the decay curve after a single doses of triamcinolone, is approximately 1.4 hr. This compares with a half-life for the enzyme from acidotic kidney of approximately 3.4 hr. Analysis of the data indicates that the induction of phosphoenolpyruvate carboxykinase activity by triamcinolone may be attributed to an increase in de novo protein synthesis. Induction by acidosis is qualitatively distinct and is partly attributed to a reduction in the rate of decay of phosphoenolpyruvate carboxykinase activity. The activities of the gluconeogenic enzymes glucose-6-phosphatase, fructose-1,6-diphosphatase, and phosphoenolpyruvate carboxykinase in both liver and kidney have been measured in animals separately treated with triamcinolone and ammonium chloride. Triamcinolone significantly increases the activities of liver phosphoenolpyruvate carboxykinase, kidney glucose-6-phosphatase, and kidney phosphoenolpyruvate carboxykinase only; ammonium chloride stimulates a 200% increase in kidney phosphoenolpyruvate carboxykinase, but has no effect on the other enzymes. The induction processes whereby triamcinolone increases phosphoenolpyruvate carboxykinase activities in liver and kidney differ quantitatively.

Acidosis↗
PubMed1993

Comparison of the kinetic properties of the pyruvate dehydrogenase complex from pig kidney cortex and medulla.

The activity of the pyruvate dehydrogenase complex (PDC) purified from pig kidney medulla was affected by K+, Na+, Cl-, HCO3-, HPO4(2-) and changes in ionic strength. Increased ionic strength influenced the activity of PDC from medulla by decreasing the Vmax and S0.5 for pyruvate and increasing the Hill coefficient. The magnitude of these changes was smaller than the corresponding changes for PDC purified from the cortex. In the presence of K+ (80 mM), Na+ (20 mM), Cl- (20 mM), HCO3- (20 mM), HPO4(2-) (10 mM) and at ionic strength of 0.15 M the S0.5 for pyruvate of PDC from medulla was 117 microM and the enzyme complex was saturated by 1.1 mM pyruvate. Under these conditions the S0.5 for pyruvate of PDC derived from cortex was 159 microM and the enzyme was saturated at 4.5 mM pyruvate. Based on the results presented in this report it is suggested that PDC in kidney medulla may be regulated not only by a phosphorylation/dephosphorylation system and end-product inhibition but also via changes in ionic strength.

Animals↗
PubMed2001

Arginine vasopressin regulates CFTR and ClC-2 mRNA expression in rat kidney cortex and medulla.

The presence of both CFTR and ClC-2 proteins in the kidney suggest that they are involved in chloride transport along the nephron but their physiological roles in this organ are not known. To further understand the role of these chloride channels we studied Wistar rats subjected to dehydration for 2 days and also the homozygous Brattleboro rats, a strain of Long-Evans rats carrying an autosomal recessive mutation that leads to a deficiency of arginine-vasopressin (AVP) secretion in the plasma. The expression of CFTR was increased in the medulla of dehydrated Wistar rats and no variation was observed in the cortex. The expression of both ClC-2 and CFTR mRNAs was low in the renal cortex and medulla of the homozygous Brattleboro rats but returned to normal levels after AVP reposition. By the use of Madine-Darby canine kidney (MDCK) type I epithelial cells, it was observed that AVP (10(-8), 10(-7) and 10(-6) M) increased CFTR mRNA expression "in vitro" but no effect was observed when changes in the medium tonicity were caused by the addition of sucrose, NaCl, manitol or urea. The modulation of both CFTR and ClC-2 mRNA by AVP, the main hormone involved in the regulation of body fluid osmolality, suggests the participation of these two chloride channels in the renal tubule transcellular chloride transport modulated by AVP.

Animals↗
PubMed1992

Regulation of pyruvate dehydrogenase kinase activity from pig kidney cortex.

The activity of pyruvate dehydrogenase (PDH) kinase in the purified PDH complex from pig kidney is sensitive to changes in ionic strength. The enzyme has optimum activity within a small range of ionic strength (0.03-0.05 M). An increase in ionic strength from 0.04 M to 0.2 M lowers the activity of PDH kinase by 32% and decreases the Km for ATP from 25 microM to 10 microM. At constant ionic strength (0.15 M) the enzyme has optimum activity over a broad pH range (7.2-8.0). The PDH kinase is stimulated 2.2-fold by 20 mM-K+, whereas Na+ even at high concentration (80 mM) has no effect on the enzyme activity. The stimulation of PDH kinase by K+ is not dependent on pH and ionic strength. PDH kinase is inhibited by HPO4(2-) in the presence of K+, whereas HPO4(2-) has no effect on the activity of this enzyme in the absence of K+. HPO4(2-) at concentrations of 2 and 10 mM inhibits PDH kinase by 28% and 55% respectively. The magnitude of this inhibition is not dependent on the ATP/ADP ratio. Inhibition by HPO4(2-) in the concentration range 0-10 mM is non-competitive with respect to ATP, and becomes mixed-type at concentrations over 10 mM. The Ki for HPO4(2-) is 10 mM. When HPO4(2-) is replaced by SO4(2-), the same effects on the activity of PDH kinase are observed. PDH kinase is also inhibited by Cl-. In the presence of 80 mM-Cl- the PDH kinase is inhibited by 40%. The inhibition by Cl- is not dependent on K+. In conclusion, we postulate that changes in phosphate concentrations may play a significant role in the regulation of PDH kinase activity in vivo.

Animals↗