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PubMed1990

Intramitochondrial pH and ammonium production in rat and dog kidney cortex.

The focus of this investigation was to compare data from isolated tubules and mitochondria of rat and dog kidneys subjected to altered medium pH (pHe) in vitro and to determine the effects of pH on ammonium production. Cytosolic pH (pHi) was determined using the fluoroprobe BCECF-AM; mitochondrial matrix pH (pHm) was estimated from the distribution of a labeled weak acid. The data indicate differences between rat and dog. pHi was consistently lower in rat than dog proximal tubules. In rat, pHm decreased in parallel with pHe and phi, accounting, at least in part, for the accelerated alpha-ketoglutarate dehydrogenase (alpha KGDH) flux, which is important in triggering increased ammoniagenesis. In dog, pHm varied to only a small extent with pHe and pHi changes. The results suggest that changes in pHm are unlikely to explain an increase in alpha KGDH flux in acute acidosis in the dog. However, pHe and pHi could conceivably lead to alterations in other factors than pHm, i.e. matrix Ca2+, which may facilitate accelerated ammonium production.

Acidosis, Renal Tubular↗
PubMed1988

Cell volume-sensitive Na+-ATPase activity in rat kidney cortex cell membranes.

A ouabain-insensitive, K+-independent, sodium pump, has been demonstrated in guinea-pig and rat kidney proximal tubular cells. This pump is thought to be distinct from the ouabain-sensitive Na+/K+ pump. We present evidence here indicating the modulation of the biochemical expression of the Na+ pump, i.e. the ouabain-insensitive Na+-ATPase, by the cell volume in rat kidney proximal tubular cells. Thus, basolateral plasma membranes from swollen cells show a ouabain-insensitive Na+-ATPase activity 10-times higher than that in membranes from control cells. If the swollen cells recover their volume, the activity decreases ten times to control values. The ouabain-sensitive Na+/K+-ATPase is not affected by changes in the cell volume.

Adenosine Triphosphatases↗
PubMed1996

The cytosolic glutathione S-transferase isoenzymes in the dog kidney cortex as compared with the corresponding MDCK renal cell line.

Cytosolic glutathione S-transferase (GST) (EC 2.5.1.18) isoenzymes of dog kidney and MDCK (an established dog renal cell line) were purified and studied. Specific GST activity was 248 and 317 nmol/min/mg protein, for dog and MDCK, respectively. Cytosolic GST was only partially purified by glutathione affinity chromatography, a substantial amount (43% and 84% for dog kidney and MDCK, respectively) of the GST activity was found in the flow-through fraction. Affinity bound GST was separated into 6 and 3 isoenzymes by anionic chromatofocusing for dog and MDCK, respectively. Flow-through GST was purified by gel filtration, anion exchange chromatography and anionic chromatofocusing showing only one GST isoenzyme, with distinct features from the affinity bound GST, for both dog and MDCK. The isoenzymes were characterized by their kinetic properties, subunit composition, specific substrates and inhibitors and immunoblot. The major dog GSTs (DII, DIV and DVI) correspond to the MDCK isoenzymes (MI, MII and MIII). Comparable pI values, a comparable affinity towards GSH and comparable sensitivities towards the inhibitors N-ethylmaleimide (NEM), triphenyltin chloride, cibacron blue and hematin were observed for the corresponding isoenzymes: DII and MI, DIV and MII, DVI and MIII. Co-electrophoresis showed that the subunit composition was identical for DII and MI, and for DIV and MII. Inhibitor and substrate sensitivities showed that the affinity bound GSTs belong to class pi and mu, the presence of class pi was confirmed by immunoblot analysis. One homodimeric GST isoenzyme was observed in the dog kidney and MDCK flow-through. Both dog and MDCK isoenzyme have a nearly neutral pI, a high affinity towards CDNB and an equal sensitivity towards triphenyltin chloride, cibacron blue and hematin. However, based on inhibitor studies and immunoblot, this isoenzyme could not be attributed to an identified GST class. The overall isoenzyme pattern of dog and MDCK affinity bound and flow through GST is comparable. The dog and MDCK affinity bound GSTs have similar characteristics and all belong to class mu or pi.

Animals↗
PubMed1988

Stimulatory action of ascorbic acid on methyl mercury-induced lipid peroxidation in rabbit kidney cortex slices.

Effects of ascorbic acid on the methylmercuric chloride (MMC)-induced lipid peroxidation and the accumulation of MMC in rabbit kidney cortical slices were studied. Ascorbic acid had a powerful stimulatory effect on the MMC-induced lipid peroxidation, while it produced only a small increase in the MMC accumulation. This results suggests that ascorbic acid increases slightly the accumulation of MMC, but that the stimulatory action of ascorbic acid on the MMC-induced lipid peroxidation cannot be explained simply by the increase in the MMC accumulation.

Animals↗
PubMed2006

Influence of polymorphisms of ABCB1 and ABCC2 on mRNA and protein expression in normal and cancerous kidney cortex.

There is increasing evidence that polymorphisms of the adenosine 5' triphosphate membrane transporters ABCB1 (P-glycoprotein, MDR1) may affect expression and function, whereas less information is available about the impact of ABCC2 (multidrug resistance-associated protein (MRP2)) single-nucleotide polymorphisms . Particularly, their role in human kidney for drug elimination and in the etiology of renal cell carcinoma is poorly understood. ABCB1 and ABCC2 mRNA and protein expression levels were determined by real-time polymerase chain reaction or immunohistochemistry in kidney cancer and adjacent unaffected cortex tissue of 82 nephrectomized renal cell cancer (RCC) patients (63 clear-cell RCC (CCRCC), 19 non-CCRCC). The DNA of all patients was genotyped for ABCB1 -2352G>A, -692T>C, 2677G>T/A (Ala893Ser/Thr), and 3435C>T, and ABCC2 -24C>T, 1249G>A (Val417Ile) and 3972C>T. ABCB1 and ABCC2 were less expressed in CCRCC than in normal cortex on mRNA as well as on protein level. Although the overall genotype frequency distribution did not differ between the patients and a matched control group, ABCB1 2677T/A and 3435T genotypes were associated with higher (P=0.02 and P=0.04) and ABCC2 -24 T with lower mRNA levels in normal tissues (0.03). The expression of ABCB1 and ABCC2 was not related to genetic variants in RCC tissue. In a reporter gene assay in HepG2 cells, the ABCC2 -24T construct showed an 18.7% reduced activity (P=0.003). In conclusion, ABCB1 and ABCC2 genotypes modulate the expression in the unaffected renal cortex of RCC patients, possibly contributing to inter-individual differences in drug and xenobiotics elimination. Their role in RCC cancer susceptibility or chemotherapy resistance needs further elucidation.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed1983

Bradykinin-stimulated differential incorporation of arachidonic acid into lipids of kidney cortex and medulla.

We investigated bradykinin-induced changes in the turnover of arachidonate in renal lipids of the perfused rabbit kidney. Upon hormone stimulation, this cellular system undergoes only transient dynamic changes in arachidonic acid metabolism; no loss of bradykinin effect on arachidonate release and prostaglandin generation is shown upon repeated hormone administrations during 8-9 hr of perfusion. Ureter-obstructed rabbit kidneys were perfused for 5-6 hr and then saline or bradykinin in saline was administered, followed after 10 sec by pulse labelling with [14C]arachidonate. The pattern of distribution of [14C]arachidonate in lipid fractions of the cortex showed that bradykinin caused a 2 to 2.5-fold increase in the relative incorporation of arachidonic acid into phosphatidylinositol (PI), phosphatidic acid (PA), diglyceride (DG) and triglyceride (TG) fractions and a concomitant decrease in its incorporation into phosphatidylcholine (PC) and phosphatidylethanolamine (PE). In contrast, in the medulla hormone administration caused a marked increase of arachidonate incorporation into PI and PC, and a decrease in incorporation into PE, PA, DG and TG. This differential arachidonate labelling of cortical vs medullary lipids following bradykinin stimulation suggests that the hormone activates different lipolytic processes in cortex and medulla, and promotes hydrolysis of arachidonic acid from different phospholipid pools.

Animals↗