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PubMed1994

cDNA cloning of a rat small-intestinal Na+/SO4(2-) cotransporter.

We have isolated a cDNA (ileal NaSi-1) from rat small intestine by homology screening with a cDNA (renal NaSi-1) encoding rat kidney cortex Na(+)-SO4(2-) cotransport. Ileal NaSi-1 cRNA specifically stimulates Na(+)-dependent SO4(2-) uptake in a time- and dose-dependent manner in Xenopus laevis oocytes, with kinetic parameters almost identical to those of the renal NaSi-1. Ileal NaSi-1 cDNA contains 2722 base pairs (bp), almost 500 bp more than the renal NaSi-1 cDNA; however, it encodes a protein of 595 amino acids identical to the renal NaSi-1 protein. Northern blot analysis shows strong signals in rat lower small intestine and kidney cortex (2.9 x 10(3) and 2.3 x 10(3) bases), with the ileal NaSi-1 corresponding to the longer transcript. We conclude that we have identified a rat ileal cDNA that encodes a membrane protein most likely involved in brush-border Na(+)-SO4(2-) cotransport. It differs to the renal NaSi-1 only in the length of the 3' untranslated region, suggesting that the major difference lies in the differential use of polyadenylation signals.

Amino Acid Sequence↗
PubMed1979

Comparative studies of cellular reactions to injuries between the inner medulla and the cortex of rat kidneys.

The inner medulla and the cortex of the rat kidney were surgically traumatized or threaded with a silk suture, and the sequence of morphologic events occurring in these two topographic locations were studied by light microscopy on Days 7, 14, and 28. On Days 7, 14, and 28 following the infliction of the surgical trauma, such cellular reactions as mononuclear cell infiltration and fibroblastic proliferation were less intense in the injured site of the inner medulla than in the cortex. Numerous foreign body type giant cells appeared about the suture material in the cortex as early as Day 7 and were persistently present on Days 14 and 28. A similar type of foreign body giant cells did not appear about the suture material within the inner medulla throughout the experiment. Our results suggest that there is a difference in cellular reaction to injury or to a foreign body between the inner medulla and the cortex of rat kidneys.

Animals↗
PubMed1999

Early increases in renal kallikrein secretion on administration of potassium or ATP-sensitive potassium channel blockers in rats.

1 This study aimed to examine whether administration of potassium or ATP-sensitive potassium channel (KATP channel) blockers caused early increases in renal kallikrein (KK) secretion. To clarify this mechanism, the effect on renal KK secretion of a KATP channel blocker was compared with the effect resulting from use of an osmotic diuretic or volume load. Furthermore, the effect on potassium-induced increases in renal KK secretion by an additional treatment using a KATP channel blocker was examined. Lastly, the effect of a KATP channel blocker on renal KK secretion was also examined in superfused slices of kidney cortex. 2 Intravenous infusion of potassium augmented renal KK secretion within 30 min while urine volume increased gradually in both the potassium loading and control groups. 3 Administration of the KATP channel blocker, 4-morpholinecarboximidine-N-1-adamantyl-N'-cyclohexylhydr ochloride (PNU-37883A) or glibenclamide, caused a dose-dependent increase in renal KK secretion. 4 The concentration of KK in urine was higher in the PNU-37883A group as compared to the osmotic-diuretic or volume-load group. 5 PNU-37883A had no additive effect on the potassium-induced increase in renal KK secretion. 6 Renal KK secretion increased in slices of kidney cortex incubated with PNU-37883A within 10 min of superfusion. 7 In conclusion, administration of both potassium and KATP channel blockers induced early increases in renal KK secretion in the absence of the washout phenomenon. Potassium loading may have increased renal KK secretion through the same mechanism as the KATP channel blocker.

Adamantane↗
PubMed1985

Effects of osmotic shocks on the ultrastructure of different tissues and cell types.

This study deals with the effects of hyper- and hypo-osmotic media on the ultrastructure of four different types of cells and tissues: rat pheochromocytoma cells of line PC12, mouse Ehrlich ascites tumor cells, rat kidney cortex and intestine. Application of hyper-osmotic conditions induces in the nuclear compartment of the tested cell types a condensation of chromatin, a ruffling of the nuclear envelope with loosening of condensed chromatin from the lamina, and an apparent loss of nucleolar fibrillar component which disappears in a background of diffuse granular material. In hypo-osmotic media, there is a marked decondensation of chromatin and a fragmentation of the granular material of the nucleolus. As far as the cytoplasmic compartment is concerned, the electron density of the cytosol is markedly increasing when going from hypo- to hyper-osmotic conditions and there is no vacuolization in hypo-osmotic media. In kidney cortex slices, application of hypo-osmotic shocks further results in a marked reduction of the extracellular space delimited by the infoldings of the tubular cells plasma membranes. These modifications are discussed in relation to the volume regulation process and the changes in ion concentration that occur in cells submitted to anisosmotic media.

Animals↗
PubMed1990

Renal arginine synthesis: studies in vitro and in vivo.

Renal arginine synthesis is a major endogenous source of arginine. Argininosuccinate lyase occurs almost exclusively in kidney cortex. In studies with isolated renal cortical tubules, we observed rapid rates of arginine synthesis from citrulline, provided a source of the N atom of the guanidino group of arginine was supplied. Aspartate, glutamate, or glutamine were effective, whereas glycine, alanine, serine, or NH4Cl were ineffective as this second substrate. Arginine synthesis as a function of citrulline concentration was determined and was found to be highly sensitive to citrulline concentrations in the physiological range (60 microM), suggesting that renal arginine synthesis in vivo could be regulated by circulating citrulline levels. Therefore, arginine synthesis by the kidney was investigated in vivo by measuring the net flux of citrulline and arginine in saline-infused (control group) and citrulline-infused rats. In normal animals, uptake of citrulline was 60.5 +/- 20.7 nmol.min-1.100 g body wt-1, and a similar arginine release was observed. Citrulline infusion that increased circulating citrulline levels fourfold resulted in a similar increase in renal citrulline uptake (224 +/- 33 nmol.min-1.100 g-1) and a similar increase in renal production of arginine. The results suggest that the availability of citrulline is a limiting factor for renal arginine synthesis in rats.

Alanine↗
PubMed1997

Hypercalcemia stimulates expression of intrarenal phospholipase A2 and prostaglandin H synthase-2 in rats. Role of angiotensin II AT1 receptors.

In chronic hypercalcemia, inhibition of thick ascending limb sodium chloride reabsorption is mediated by elevated intrarenal PGE2. The mechanisms and source of elevated PGE2 in hypercalcemia are not known. We determined the effect of hypercalcemia on intrarenal expression of cytosolic phospholipase A2 (cPLA2), prostaglandin H synthase-1 (PGHS-1), and prostaglandin H synthase-2 (PGHS-2), enzymes important in prostaglandin production. In rats fed dihydrotachysterol to induce hypercalcemia, Western blot analysis revealed significant upregulation of both cPLA2 and PGHS-2 in the kidney cortex and the inner and outer medulla. Immunofluorescence localized intrarenal cPLA2 and PGHS-2 to interstitial cells of the inner and outer medulla, and to macula densa and cortical thick ascending limbs in both control and hypercalcemic rats. Hypercalcemia had no effect on intrarenal expression of PGHS-1. To determine if AT1 angiotensin II receptor activation was involved in the stimulation of cPLA2 and PGHS-2 in hypercalcemia, we treated rats with the AT1 receptor antagonist, losartan. Losartan abolished the polydipsia associated with hypercalcemia, prevented the increase in cPLA2 protein in all regions of the kidney, and diminished PGHS-2 expression in the inner medulla. In addition, losartan completely prevented the increase in urinary PGE2 excretion in hypercalcemic rats. Intrarenal levels of angiotensin II were unchanged in hypercalcemia. These data indicate that hypercalcemia stimulates intrarenal cPLA2 and PGHS-2 protein expression. Our results further support a role for angiotensin II, acting on AT1 receptors, in mediating this stimulation.

Angiotensin II↗
PubMed2000

Purification, characterization, and localization of an ATP diphosphohydrolase in porcine kidney.

Membranes of pig kidney cortex tissue were solubilized in the presence of Triton X-100. Partial purification of ATP diphosphohydrolase (ATPDase) was achieved by successive chromatography on concanavalin A-Sepharose, Q-Sepharose Fast Flow, and 5'-AMP-Sepharose 4B. Monoclonal antibodies against ATPDase were generated. Further purification of the ATPDase was obtained by immunoaffinity chromatography with these monoclonal antibodies. NH(2)-terminal amino acid sequencing of the 78-kDa protein showed a sequence very homologous to mammalian CD39. The protein is highly glycosylated, with a nominal molecular mass of approximately 57 kDa. The purified enzyme hydrolyzed di- and triphosphates of adenosine, guanosine, cytidine, uridine, inosine, and thymidine, but AMP and diadenosine polyphosphates could not serve as substrates. All enzyme activities were dependent on divalent cations and were partially inhibited by 10 mM sodium azide. The distribution of the enzyme in pig kidney cortex was examined immunohistochemically. The enzyme was found to be present in blood vessel walls of glomerular and peritubular capillaries.

Amino Acid Sequence↗
PubMed2000

Apoptosis in renal proximal tubules of rats treated with low doses of aminoglycosides.

Kidney cortex apoptosis was studied with female Wistar rats treated for 10 days with gentamicin and netilmicin at daily doses of 10 or 20 mg/kg of body weight and amikacin or isepamicin at daily doses of 40 mg/kg. Apoptosis was detected and quantitated using cytological (methyl green-pyronine) and immunohistochemical (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) staining, in parallel with a measurement of drug-induced phospholipidosis (cortical phospholipids and phospholipiduria), cortical proliferative response ((3)H incorporation in DNA and histoautoradiography after in vivo pulse-labeling with [(3)H]thymidine), and kidney dysfunction (blood urea nitrogen and creatinine). Gentamicin induced in proximal tubules a marked apoptotic reaction which (i) was detectable after 4 days of treatment but was most conspicuous after 10 days, (ii) was dose dependent, (iii) occurred in the absence of necrosis, and (iv) was nonlinearly correlated with the proliferative response (tubular and peritubular cells). Comparative studies revealed a parallelism among the extents of phospholipidosis, apoptosis, and proliferative response for three aminoglycosides (gentamicin >> amikacin congruent with isepamicin). By contrast, netilmicin induced a marked phospholipidosis but a moderate apoptosis and proliferative response. We conclude that rats treated with gentamicin develop an apoptotic process as part of the various cortical alterations induced by this antibiotic at low doses. Netilmicin, and still more amikacin and isepamicin, appears safer in this respect. Whereas a relation between aminoglycoside-induced tubular apoptosis and cortical proliferative response seems to be established, no simple correlation with phospholipidosis can be drawn.

Amikacin↗
PubMed1994

Lack of biologic activity or specific binding of amino-terminal pro-ANP segments in the rat.

In addition to atrial natriuretic peptide (ANP99-126) itself, linear peptide fragments from its N-terminal prohormone segment (pro-ANP) have been reported to have biological activity. In vivo, diuresis and natriuresis, as well as hypotension have been observed. In vitro, sodium uptake into medullary collecting duct cells was inhibited, and tone of vascular smooth muscle was reduced, associated with activation of guanylate cyclase. Such previous studies have used heterologous peptides and species, e.g., human pro-ANP1-30 or pro-ANP31-67, tested in rat, pig, or dog. The present experiments were designed to test whether rat pro-ANP1-30 or pro-ANP31-67 were natriuretic and hypotensive in rats, whether the two peptides showed specific binding to plasma membranes from rat kidney cortex or aorta, and whether they affected particulate guanylate cyclase activity in rat glomerular membranes. To extend in vitro results from the literature, the effect of human pro-ANP31-67 on transport in the rat medullary collecting duct in vivo was also tested. Although rat ANP99-126, as expected, increased diuresis and natriuresis, associated with inhibition of transport in the medullary collecting duct, in identically treated rats human pro-ANP31-67 was without effect. Similarly, only the ANP99-126 infusion resulted in reduction of arterial blood pressure. Furthermore, no diuretic, natriuretic, or hypotensive responses were observed in rats infused with either rat pro-ANP31-67 or pro-ANP1-30. In plasma membranes from rat kidney cortex or aorta, neither of the rat prosegments showed specific binding, or interference with ANP99-126 receptors. Finally, in contrast to ANP99-126, neither of the prosegments was able to increase basal guanylate cyclase activity in rat glomerular membranes. Therefore, under our experimental conditions we were unable to replicate the earlier results. This study thus does not support a regulatory role for pro-ANP fragments in blood volume or blood pressure homeostasis.

Amino Acid Sequence↗
PubMed1990

Renal antigens in mercuric chloride induced, anti-GBM autoantibody glomerular disease.

Two antibody probes were used to characterize the putative renal antigens of HgCl2-induced antiglomerular basement membrane renal disease in Brown Norway (BN) rat. The first probe was the linear immunofluorescence imparting, in vivo bound, nephritogenic antiglomerular-basement-membrane autoantibody (anti-GBM-Ab). The second probe was a rat monoclonal antibody to the B subunit of laminin that was obtained from fusion of spleen cells of HgCl2 injected BN rat. By enzyme-linked immunosorbent assay (ELISA) the anti-GBM-Ab reacted with laminin, type IV collagen, collagenase-resistant noncollagenous portion of glomerular basement membrane (GBM), saline soluble proteins of kidney cortex homogenate and fibronectin. Western blot analysis of laminin indicated that the reactive epitopes detected by both probes were on the B chain subunit but not the A subunit. In nonreduced collagenase-digested GBM the epitopes were present on 27 kD and 42 to 48 kD polypeptides. A similar pattern was seen on collagenase-digested human GBM. On rat and human GBM the patterns obtained with rat autoantibody and autoantibody from a patient with Goodpasture syndrome were similar, suggesting that some of the in vivo bound anti-GBM autoantibodies in HgCl2-induced disease in rat are directed against epitopes which are similar to the Goodpasture antigen of human. Reactive epitopes were also detected on saline soluble proteins of kidney cortex homogenate with the predominant antigen being a 31 kD polypeptide. In the saline soluble proteins the reactive polypeptides including the major 31 kD polypeptide did not originate from laminin, type IV collagen, or the collagenase-resistant noncollagenous part of GBM. The precise structural origin of soluble proteins was not defined.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Characterization of cytochromes P450 in liver and kidney of rats treated with di-(2-ethylhexyl)phthalate.

A polyclonal antibody was made to a liver cytochrome P450 purified from di-(2-ethyl-hexyl)phthalate (DEHP)-treated Sprague-Dawley rats and was used to identify the CYP4A forms in liver and kidney cortex microsomes of control rats and rats treated with this peroxisome proliferator. Three clearly separated major protein bands were recognized on western blots in liver microsomes of control male rats or male rats treated with a single dose of DEHP, which, based on the description of relative mobility, tissue specificity, and sex dependent expression of CYP4A forms (Sundseth and Waxman (1992). J. Biol. Chem., 267, 801-810), correspond to the migration pattern of forms 4A1, 4A2, and 4A3 in clofibrate-treated rats. The administration of DEHP for 2 or 3 days caused a loss of resolution of two of the protein bands. The protein band corresponding to 4A2 was absent in liver or kidney cortex microsomes of DEHP-treated or control female rats and was not always visible in the livers of control male rats. The purified P450DEHP supported the hydroxylation of arachidonic acid at both the 19- and 20-carbon atoms with turnover rates of 1.4 +/- 0.2 and 22.7 +/- 2.5 nmoles per minute per nmol P450, respectively. No measurable amounts of hydroxylated products were obtained when prostaglandin E1, leukotriene B4, or testosterone were used as substrates. Another member of the CYP4 family, 4B1 from rabbit lung microsomes, was also recognized by this antibody on western blot analysis; however, rabbit lung form 4A4 showed only minimal cross-reactivity with this antibody.

Animals↗
PubMed1996

Adrenal steroids stimulate thiazide-sensitive NaCl transport by rat renal distal tubules.

The current experiments were designed to test the hypothesis that adrenal steroids increase thiazide-sensitive Na and Cl transport by the mammalian renal distal convoluted tubule (DCT). Male Sprague-Dawley rats were adrenalectomized and received steroid hormones by osmotic pumps. Six groups of animals were studied as follows: group I, no hormones; group II, replacement levels of dexamethasone only; group III, replacement levels of aldosterone only; group IV, replacement levels of both hormones; group V; replacement levels of aldosterone and high levels of dexamethasone; and group VI, replacement levels of dexamethasone and high levels of aldosterone. Circulating levels of both hormones were found to be in the high physiological range when infused at the high rate. In vivo microperfusion of distal tubules was performed to determine rates of Na and Cl transport. Chlorothiazide was used to assess the magnitude of electroneutral Na-Cl cotransport. Both aldosterone and dexamethasone stimulated thiazide-sensitive Na and Cl transport by the distal tubule by more than fivefold. [3H]metolazone binding was measured to assess the number of thiazide-sensitive Na-Cl cotransporters in renal cortex. Each steroid also increased the number of [3H]metolazone binding sites in kidney cortex more than threefold. The results are consistent with the presence of both mineralocorticoid and glucocorticoid receptors in the mammalian DCT. Physiological changes in circulating levels of adrenal steroids may affect renal NaCl excretion in part by regulating the rate of electroneutral Na-Cl absorption by the DCT.

Adrenalectomy↗
PubMed1978

The ontogeny of sugar transport in kidney.

Concentrative uptake of alpha-methyl-d-glucoside (AMG) by isolated renal tubule fragments from the newborn Sprague-Dawley rat has been demonstrated and the validity of this phenomenon confirmed by an in vivo demonstration of AMG uptake by the newborn kidney cortex. A kinetic analysis of the entry phenomenon in the newborn tubule reveals the presence of two distinct membrame transport systems for AMG, only one of which is present in the adult tubule. All transport of sugar in both newborn and adult tubules was phlorizin-sensitive, but was only partially ingibited in Na+-free buffer. Glucose was shown to inhibit uptake competitively on the shared, high capacity system. Uptake on the high affinity system in the newborn represents 15-20% of the total at physiologic sugar concentrations. It is concluded that active sugar transport is a characteristic of the newborn rat kidney and that the isolated tubule preparation is a more accurate reflection of this phenomenon than is the renal cortical slice.

Age Factors↗
PubMed1990

cDNA cloning and expression in Xenopus laevis oocytes of pig renal dipeptidase, a glycosyl-phosphatidylinositol-anchored ectoenzyme.

Clones expressing renal dipeptidase (EC 3.4.13.11) have been isolated from a pig kidney cortex cDNA library after employing the polymerase chain reaction technique to amplify a region of the dipeptidase cDNA. The complete primary sequence of the enzyme has been deduced from a full length cDNA clone. This predicts a protein of 409 amino acids, a cleavable N-terminal signal sequence of 16 residues and two N-linked glycosylation sites. At the C-terminus of the predicted sequence is a stretch of mainly hydrophobic amino acids which is presumed to direct the attachment of the glycosyl-phosphatidylinositol membrane anchor. Expression of the mRNA for pig renal dipeptidase in Xenopus laevis oocytes led to the production of a disulphide-linked dimeric protein of subunit Mr 48,600 which was recognized by a polyclonal antiserum raised to renal dipeptidase purified from pig kidney cortex. Bacterial phosphatidylinositol-specific phospholipase C released renal dipeptidase from the surface of the oocytes and converted the amphipathic detergent-solubilized form of the dipeptidase to a hydrophilic form, indicating that Xenopus laevis oocytes can process expressed proteins to their glycosyl-phosphatidylinositol anchored form.

Amino Acid Sequence↗
PubMed2000

Time course of arsenite-induced copper accumulation in rat kidney.

Oral administration of inorganic arsenic has been shown to lead to an accumulation of copper in the kidneys of rats and guinea pigs. However, nothing is known about the characteristics and mechanisms of this organ-specific renal copper accumulation. Many heavy metals accumulate in the kidney, either after environmental or occupational exposure. An additional accumulation of any other trace metals, even essential ones, may therefore be critical for that organ. This prompted us to follow the course of the renal copper accumulation. Rats were given daily subcutaneous doses of sodium arsenite for 12 d. Each second day, three rats were killed by exsanguination and the liver, kidneys, and blood removed and analysed for As, Cu, and other trace elements by atomic emission spectrometry. Results indicate that arsenic and copper accumulate in the kidney cortex synchroneously over time. Arsenic also accumulated in the liver and red blood cells (RBC). Copper levels in the RBC and liver as well as copper excretion into the urine were unaffected. After terminating arsenite administration, there was a slow decline in tissue levels of both arsenic and copper, a phenomenon which was parallel for both metals. Because the copper level in the liver was not affected, it is concluded from this study that renal processes and not hepatic or biliary mechanisms might be responsible for the renal copper accumulation. Furthermore, the strong linear correlation (r = 0.85) between arsenic and copper levels in the kidney during and after arsenite administration suggests a functional relationship between arsenic and copper with respect to their retention in the kidney.

Animals↗
PubMed2006

Ifosfamide-induced nephrotoxicity: mechanism and prevention.

The efficacy of ifosfamide (IFO), an antineoplastic drug, is severely limited by a high incidence of nephrotoxicity of unknown etiology. We hypothesized that inhibition of complex I (C-I) by chloroacetaldehyde (CAA), a metabolite of IFO, is the chief cause of nephrotoxicity, and that agmatine (AGM), which we found to augment mitochondrial oxidative phosphorylation and beta-oxidation, would prevent nephrotoxicity. Our model system was isolated mitochondria obtained from the kidney cortex of rats treated with IFO or IFO + AGM. Oxidative phosphorylation was determined with electron donors specific to complexes I, II, III, or IV (C-I, C-II, C-III, or C-IV, respectively). A parallel study was done with (13)C-labeled pyruvate to assess metabolic dysfunction. Ifosfamide treatment significantly inhibited oxidative phosphorylation with only C-I substrates. Inhibition of C-I was associated with a significant elevation of [NADH], depletion of [NAD], and decreased flux through pyruvate dehydrogenase and the TCA cycle. However, administration of AGM with IFO increased [cyclic AMP (cAMP)] and prevented IFO-induced inhibition of C-I. In vitro studies with various metabolites of IFO showed that only CAA inhibited C-I, even with supplementation with 2-mercaptoethane sulfonic acid. Following IFO treatment daily for 5 days with 50 mg/kg, the level of CAA in the renal cortex was approximately 15 micromol/L. Taken together, these observations support the hypothesis that CAA is accumulated in renal cortex and is responsible for nephrotoxicity. AGM may be protective by increasing tissue [cAMP], which phosphorylates NADH:oxidoreductase. The current findings may have an important implication for the prevention of IFO-induced nephrotoxicity and/or mitochondrial diseases secondary to defective C-I.

Acetaldehyde↗
PubMed1995

Effect of P2Y-purinoceptor stimulation on renal gluconeogenesis in rats.

In the freshly prepared rat renal cortical tubule suspension, the effects of ATP on intracellular free calcium mobilization and gluconeogenesis were investigated. ATP increased intracellular free calcium concentration ([Ca2+]i) in a dose-dependent manner (10(-6) - 10(-3) M). The rank order in the potency of ATP analogs at 10(-4) M was 2-methylthio ATP > ATP > or = ADP. AMP, adenosine and alpha, beta-methylene ATP did not respond to [Ca2+]i. These results suggest that P2-purinoceptor in the rat kidney cortex should be specifically P2Y subtype. Renal gluconeogenesis from pyruvate was stimulated maximally by 10(-4) M ATP (48.3 +/- 13.2%). This effect was significantly inhibited by 10(-4) M suramin. Thus, the present study suggests that renal gluconeogenesis is increased via P2Y-specific purinoceptor stimulation.

Adenine Nucleotides↗
PubMed1988

Renal microsomal cytochrome P-450 and the oxidative metabolism of arachidonic acid.

Arachidonic acid is oxidized by the microsomal cytochrome P-450 monooxygenases of rabbit kidney cortex and medulla to products that include W and W-1 alcohols and several epoxyacids. In vivo administration of deoxycorticosterone acetate results in a time dependent and selective induction of the arachidonic acid W/W-1 oxygenase activity of cortex and medulla microsomal fractions (145% and 220% of controls, respectively). Initial segmental analysis shows the presence of an active epoxygenase activity in the isolated rabbit pars recta and its in vitro activation by p-aminohippuric acid.

Animals↗