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PubMed2004

Mouse reduced in osteosclerosis transporter functions as an organic anion transporter 3 and is localized at abluminal membrane of blood-brain barrier.

The "reduced in osteosclerosis" transporter (Roct), which shows decreased expression in the osteosclerosis (oc) mutant mouse, has high homology with rat and human organic anion transporter 3 (OAT3). However, its transport properties and involvement in bone turnover are poorly understood. Here, we examined Roct-mediated transport using a Xenopus laevis oocyte expression system. Roct-expressing oocytes exhibited uptake of [(3)H]estrone sulfate, [(3)H]p-aminohippuric acid, [(3)H]benzylpenicillin, [(3)H]estradiol 17beta-glucronide, [(3)H]indoxyl sulfate, [(14)C]indomethacin, [(3)H]homovanillic acid, [(3)H]cimetidine, [(14)C]glutarate, [(14)C]salicylic acid, and [(3)H]methotrexate. Furthermore, the uptake of [(3)H]benzylpenicillin by Roct coexpressed with Na(+)-dicarboxylate cotransporter was trans-stimulated by glutarate preloading, and [(3)H]estrone sulfate uptake showed a similar tendency, suggesting that Roct is a dicarboxylate exchanger. [(3)H]Benzylpenicillin uptake by Roct was inhibited by OAT3 substrates and inhibitors, and by sulfate or glucuronide conjugates, and compounds involved in bone turnover. Roct mRNA is expressed abundantly in the kidney and was also detected in the brain, choroid plexus, and eye. Immunohistochemical analysis revealed that Roct is localized in brain capillary endothelial cells. These results indicate that the transport properties and tissue distribution of Roct are similar to those of OAT3, suggesting that Roct functions as mouse OAT3. Because Roct is expressed in the kidney and at the blood-brain barrier, it may play a role in the excretion of substrates such as conjugates and bone turnover factors.

Animals↗
PubMed2002

Identification of a mechanism by which the methylmercury antidotes N-acetylcysteine and dimercaptopropanesulfonate enhance urinary metal excretion: transport by the renal organic anion transporter-1.

N-Acetylcysteine (NAC) and dimercaptopropanesulfonate (DMPS) are sulfhydryl-containing compounds that produce a dramatic acceleration of urinary methylmercury (MeHg) excretion in poisoned animals, but the molecular mechanism for this effect is unknown. NAC and DMPS are themselves excreted in urine in high concentrations. The present study tested the hypothesis that the complexes formed between MeHg and these anionic chelating agents are transported from blood into proximal tubule cells by the basolateral membrane organic anion transporters (Oat) 1 and Oat3. Xenopus laevis oocytes expressing rat Oat1 showed increased uptake of [(14)C]MeHg when complexed with either NAC or DMPS but not when complexed with L-cysteine, glutathione, dimercaptosuccinate, penicillamine, or gamma-glutamylcysteine. In contrast, none of these MeHg complexes were transported by Oat3-expressing oocytes. The apparent K(m) values for Oat1-mediated transport were 31 +/- 2 microM for MeHg-NAC and 9 +/- 2 microM for MeHg-DMPS, indicating that these are relatively high-affinity substrates. Oat1-mediated uptake of [(14)C]MeHg-NAC and [(14)C]MeHg-DMPS was inhibited by prototypical substrates for Oat1, including p-aminohippurate (PAH), and was trans-stimulated when oocytes were preloaded with 2 mM glutarate but not glutamate. Conversely, efflux of [(3)H]PAH from Oat1-expressing oocytes was trans-stimulated by glutarate, PAH, NAC, DMPS, MeHg-NAC, MeHg-DMPS, and a mercapturic acid, indicating that these are transported solutes. [(3)H]PAH uptake was competitively inhibited by NAC (K(i) of 2.0 +/- 0.3 mM) and DMPS (K(i) of 0.10 +/- 0.02 mM), providing further evidence that these chelating agents are substrates for Oat1. These results indicate that the MeHg antidotes NAC and DMPS and their mercaptide complexes are transported by Oat1 but are comparatively poor substrates for Oat3. This is the first molecular identification of a transport mechanism by which these antidotes may enhance urinary excretion of toxic metals.

Acetylcysteine↗
PubMed2003

Human renal organic anion transporter 1-dependent uptake and toxicity of mercuric-thiol conjugates in Madin-Darby canine kidney cells.

Mercuric ions are highly reactive and form a variety of organic complexes or conjugates in vivo. The renal proximal tubule is a primary target for mercury uptake and toxicity, and circumstantial evidence implicates organic anion transporters in these processes. To test this hypothesis directly, the transport and toxicity of mercuric-thiol conjugates were characterized in a Madin-Darby canine kidney cell line stably transfected with the human organic anion transporter 1 (hOAT1). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-terazolium bromide assays (for mitochondrial dehydrogenase) confirmed that mercuric conjugates of the thiols N-acetylcysteine (NAC), cysteine, or glutathione were more toxic in hOAT1-transfected cells than in the nontransfected cells. The NAC-Hg(2+) conjugate was most cytotoxic, inducing greater than 50% cellular death over 18 h at a concentration of 100 microM. The cytotoxic effects were fully reversed by probenecid (an OAT1 inhibitor) and partially reversed by p-aminohippurate (an OAT1 substrate). Toxicity of this conjugate was reduced by the OAT1-exchangeable dicarboxylates alpha-ketoglutarate, glutarate, and adipate, but not by succinate, a nonexchangeable dicarboxylate. (203)Hg-uptake studies showed probenecid-sensitive uptake of mercury-thiol conjugates in the hOAT1-transfected cells. The apparent K(m) for the NAC-Hg(2+) conjugate was 44 +/- 9 microM. Uptake of the NAC-Hg(2+) conjugate was cis-inhibited by glutarate, but not by methylsuccinate, paralleling their effects on toxicity. Probenecid-sensitive transport of the NAC-Hg(2+) conjugate was also shown to occur in Xenopus laevis oocytes expressing the hOAT1 or the rOAT3 transporters, suggesting that OAT3 may also transport thiol-Hg(2+) conjugates. Thus, renal accumulation and toxicity of thiol-Hg(2+) conjugates may depend in part on the activity of the organic transport system.

Animals↗
PubMed2001

Expression of a Pseudomonas putida aminotransferase involved in lysine catabolism is induced in the rhizosphere.

Using a transposon carrying a promoterless lux operon to generate transcriptional fusions by insertional mutagenesis, we have identified a Pseudomonas putida gene with increased expression in the presence of corn root exudates. Expression of the transcriptional fusion, induced by the amino acid lysine, was detected in P. putida in the rhizosphere of plants as well as in response to seed exudates. The mutant was unable to grow on lysine or delta-aminovalerate as carbon sources, which indicates that the affected function is involved in the pathway for lysine catabolism. However, the mutant strain grew with glutaric acid, the product of delta-aminovalerate metabolism via glutaric acid semialdehyde, as a C source. The translated sequence of the interrupted gene showed high levels of similarity with aminotransferases. These sets of data suggest that the product of this gene has delta-aminovalerate aminotransferase activity. This is the first direct genetic evidence correlating a DNA sequence with such activity in Pseudomonadaceae.

DNA Transposable Elements↗
PubMed1993

Immunoblotting as a confirmatory test for antimitochondrial antibodies in primary biliary cirrhosis.

Primary biliary cirrhosis is characterised by the presence of antimitochondrial antibodies which are directed against components of mitochondrial dehydrogenase complexes. The specificity of antimitochondrial antibodies for primary biliary cirrhosis as detected by immunoblotting was investigated. Commercially available preparations of pyruvate and oxo-glutarate dehydrogenases and beef-heart mitochondria were used as source of antigens. Sera from 47 primary biliary cirrhosis patients (46 of whom were antimitochondrial antibody positive by immunofluorescence), 16 non-primary biliary cirrhosis patients (antimitochondrial antibody positive by immunofluorescence), 23 liver-kidney microsomal antibody positive chronic active hepatitis patients, and 32 patients with connective tissue diseases were examined. Of the 47 subjects with primary biliary cirrhosis, 43 (91%) and 13 (28%) tested positive by immunoblotting for pyruvate and oxo-glutarate dehydrogenase, respectively. Only three primary biliary cirrhosis patients were negative for both antigens, including the only one shown to be antimitochondrial antibody negative by immunofluorescence. The other two patients were positive by immunoblotting with beef-heart mitochondria. In contrast, only three of 16 (19%) non-primary biliary cirrhosis patients who were antimitochondrial antibody positive by immunofluorescence tested positive by immunoblotting (for both pyruvate dehydrogenase and beef-heart mitochondria). None of the 23 liver-kidney microsomal antibody positive and the 32 patients with rheumatic diseases were positive by immunoblotting with any antigen. Our data show that immunoblotting with commercially available oxo-acid dehydrogenases is a reproducible method for the detection of antimitochondrial antibodies highly specific for primary biliary cirrhosis.

Adult↗
PubMed1983

Alpha-ketoglutarate metabolism by cytochrome-containing anaerobes.

During growth in the presence of tracer amounts of exogenously supplied alpha-keto[1-14C]glutarate (AKG) or alpha-keto [5-14C]glutarate, cytochrome-containing Bacteroides fragilis strain 2044 and Bacteroides vulgatus strain 8482 incorporated extremely small amounts of radioactivity into cell macromolecules and protoheme. Under identical conditions, Bacteroides "l" strain 7CM and Bacteroides buccae strain J1 incorporated substantial label from [5-14C]AKG, but not [1-14C]AKG, into cellular macromolecules and protoheme. Bacteroides succinogenes strain S85 incorporated radioactivity from both [1-14C]AKG and [5-14C]AKG into cell macromolecules, but only label from [5-14C]AKG appeared in protoheme. Selenomonas ruminantium strain HD1 and Butyrivibrio fibrisolvens strain D1, both of which are devoid of cytochromes, incorporated substantial label from both [1-14C]AKG and [5-14C]AKG into cell macromolecules, but failed to incorporate label from either position into protoheme. Bacteroides ruminicola sp. brevis strain GA33 incorporated label from both [1-14C]AKG and [5-14C]AKG into both cell macromolecules and protoheme. A substantial portion of the heme synthesized by this organism may be formed by the "plant" pathway involving the intact use of the AKG carbon skeleton. Major differences exist in the manner and extent of AKG utilization among cytochrome-containing anaerobes and between these organisms and bacteria devoid of cytochromes obtained from similar environments.

Bacteroides↗
PubMed2003

Stoichiometry of organic anion/dicarboxylate exchange in membrane vesicles from rat renal cortex and hOAT1-expressing cells.

Although membrane vesicle studies have established the driving forces that mediate renal organic anion secretion and the organic anion transporter Oat1 has now been cloned in several species, its stoichiometry has remained uncertain. In this study, we used electrophysiology, kinetic measurements, and static head experiments to determine the coupling ratio for Oat1-mediated organic anion/dicarboxylate exchange. Initial experiments demonstrated that uptake of PAH by voltage-clamped Xenopus laevis oocytes expressing rOat1 led to net entry of positive charge, suggesting that coupling was one-to-one. This conclusion was confirmed by kinetic analysis of PAH and glutarate fluxes in native basolateral membrane vesicles from the rat renal cortex, which showed a Hill coefficient of 1. Similarly, static head experiments on the rat vesicles also showed a 1:1 coupling ratio. To confirm these conclusions in a system expressing a single cloned transporter, Madin-Darby canine kidney cells were stably transfected with the human exchanger hOAT1. The hOAT1-expressing cell line showed extensive PAH transport, which was very similar in all respects to transport expressed by hOAT1 in Xenopus oocytes. Its Km for PAH was 8 microM and glutarate effectively trans-stimulated PAH transport. When stoichiometry was assessed using plasma membranes isolated from the hOAT1-expressing cells, both kinetic and static head data indicated that hOAT1 also demonstrated a 1:1 coupling between organic anion and dicarboxylate.

Animals↗
PubMed2004

Substrate specificity of the human renal sodium dicarboxylate cotransporter, hNaDC-3, under voltage-clamp conditions.

Proximal tubule cells extract dicarboxylates from filtrate and blood, using cotransporters located in the brush border [sodium dicarboxylate cotransporter (NaDC-1)] and basolateral cell membrane (NaDC-3). We expressed the human NaDC-3 (hNaDC-3) in Xenopus laevis oocytes and characterized it by the two-electrode voltage-clamp technique. At -60 mV, succinate (4 carbons) and glutarate (5 carbons) generated inward currents due to translocation of three sodium ions and one divalent dicarboxylate, whereas oxalate (2 carbons) and malonate (3 carbons) did not. The cis-dicarboxylate maleate produced currents smaller in magnitude, whereas the trans-dicarboxylate fumarate generated currents similar to succinate. The substituted succinate derivatives, malate, 2,2- and 2,3-dimethylsuccinate, and 2,3-dimercaptosuccinate elicited inward currents, whereas aspartate and guanidinosuccinate showed hardly detectable currents. The C-5 dicarboxylates glutarate and alpha-ketoglutarate produced larger currents than succinate; glutamate and folate failed to cause inward currents. Kinetic analysis revealed, at -60 mV, K(0.5) values of 25 +/- 12 microM for succinate and 45 +/- 13 microM for alpha-ketoglutarate, values close to the plasma concentration of these compounds. For both compounds, the K(0.5) was independent of voltage, whereas the maximal current increased with hyperpolarization. As opposed to the rat and flounder orthologs, hNaDC-3 was hardly inhibited by lithium concentrations up to 5 mM. In the absence of sodium, however, lithium can mediate succinate-dependent currents. The narrow substrate specificity prevents interaction of drugs with dicarboxylate-like structure with hNaDC-3 and ensures sufficient support of the proximal tubule cells with alpha-ketoglutarate for anion secretion via organic anion transporter 1 or 3.

Animals↗
PubMed2006

Crystal engineering of analogous and homologous organic compounds: hydrogen bonding patterns in trimethoprim hydrogen phthalate and trimethoprim hydrogen adipate.

BACKGROUND: Trimethoprim [2,4-diamino-5-(3',4',5'-trimethoxybenzyl)pyrimidine] is an antifolate drug. It selectively inhibits the bacterial dihydrofolate reductase (DHFR) enzyme. RESULTS: In the crystal structures of trimethoprim (TMP)-hydrogen phthalate (1) and trimethoprim-hydrogen adipate (2), one of the N atoms of the pyrimidine ring is protonated and it interacts with the deprotonated carboxylate oxygens through a pair of nearly parallel N-H...O hydrogen bonds to form a fork-like interaction. In the compound 1, the pyrimidine moieties of the TMP cations are centrosymmetrically paired through a pair of N-H...N hydrogen bonds involving 4-amino group and the N (N3) atom of the pyrimidine rings to form a 8-membered hydrogen bonded ring [R2(2)(8)]. The 4-amino group of one TMP moiety and 2-amino group of another TMP moiety (both moieties are members of a base pair) are bridged by the carbonyl oxygen of the phthalate moiety through N-H...O hydrogen bonds forming 8-membered hydrogen-bonded ring [R2(2)(8)]. The characteristic hydrogen-bonded rings observed in the structure aggregate into a supramolecular ladder consisting of a pair of chains, each of which is built up of alternate TMP and hydrogen phthalate ions. In the compound 2, two TMP cations and two hydrogen adipate anions are arranged about an inversion center so that the complementary DDAA (D = donor, A = acceptor) arrays of quadruple hydrogen-bonding patterns are formed. The head-to-tail arrangement of the hydrogen adipate ions leads to a hydrogen-bonded supramolecular chain. From crystal engineering point of view, it is interesting to note that the compound 1 has a hydrogen-bonded network remarkably identical with its aliphatic analogue, trimethoprim hydrogen maleate. Similarly the compound 2, resembles its homolog trimethoprim hydrogen glutarate. CONCLUSION: In the crystal structure of trimethoprim hydrogen phthalate, the hydrogen-bonded network is remarkably identical with its aliphatic analogue, trimethoprim hydrogen maleate. Similarly in the crystal structure of trimethoprim hydrogen adipate the hydrogen bonded network resembles its homolog trimethoprim hydrogen glutarate.

Journal Article↗
PubMed1982

C6-C10-dicarboxylic aciduria: investigations of a patient with riboflavin responsive multiple acyl-CoA dehydrogenation defects.

The abnormal metabolites-adipic, suberic, and sebacic acids-were detected in large amounts in the urine of a boy during a Reye's syndrome-like crisis. Substantial amounts of 5-OH-caproic acid, caproylglycine, glutaric acid, and 3-OH-butyric acid and moderately elevated amounts of ethylmalonic acid, methylsuccinic acid, 3-OH-isovaleric acid, and isovalerylglycine were also found. These metabolites were consistently present in urine samples collected in the boy's habitual condition after the attack. 1-[14C]-Palmitic acid was oxidized at a normal rate, whereas U-[14C]-Palmitic acid was oxidized at a reduced rate in cultured skin fibroblasts from the patient, thus indicating a defect at the level of medium- and/or short-chain fatty acid oxidation. Riboflavin medication (100 mg three times a day) significantly reduced the excreted amounts of pathologic metabolites, suggesting a flavineadeninedinucleotide-related acyl-CoA dehydrogenation defect as the cause of the disease. Carnitine in plasma was low in the patient (6 mumole/liter, controls 26-74 mumole/liter), suggesting carnitine deficiency as a secondary effect of the acyl-CoA dehydrogenation deficiency. The present patient, who presented with a Reye's syndrome-like attack, suffers from impaired dehydrogenation of acyl-CoA resulting in accumulation of acyl-CoA in the cells. Attacks with similar symptoms are seen in other acyl-CoA dehydrogenation deficiencies, such as glutaric aciduria types I and II, other types of C6-C10-dicarboxylic acidurias and isovaleric acidemia. Reduced flow through the acyl-CoA dehydrogenation steps may therefore be an ethiologic factor in Reye's syndrome. Several of the accumulated acyl-CoA's are toxic and may be responsible for some of the symptoms. The low carnitine level in plasma and the elevated esterified carnitine excretion in the present patient indicate that acyl-CoA accumulation may cause a functional carnitine deficiency by sequestration of carnitine as acyl-carnitines. As the inborn defect, systemic carnitine deficiency may exhibit symptoms like those of Reye's syndrome, it may be speculated whether functional carnitine deficiency in patients with accumulated acyl-CoA is another causal factor in the development of the symptoms during attacks.

Acyl Coenzyme A↗
PubMed2005

Transport mechanism and substrate specificity of human organic anion transporter 2 (hOat2 [SLC22A7]).

Human organic anion transporter 2 (hOat2[SLC22A7]) is highly expressed in the human liver. Although localization, gene expression, substrate specificity and transport mechanisms of other human Oat isoforms such as human Oat1 (hOat1), human Oat3 (hOat3) and human Oat4 (hOat4) have been elucidated, information concerning human Oat2 (hOat2) is less defined. The objective of this study was to provide further information on the transport mechanism and substrate specificity of hOat2. When expressed in Xenopus laevis oocytes, the transport of organic compounds mediated by hOat2 was not affected by the replacement of extracellular sodium with lithium, choline and mannitol. The uptake of estrone sulfate (ES) in hOat2-expressing oocytes was significantly trans-stimulated by preloading the oocytes with fumarate and succinate, but not glutarate. Moreover, we observed that hOat2 mediates the transport of bumetanide, ES, glutarate, dehydroepiandrosterone sulfate, allopurinol, prostaglandin E2, 5-fluorouracil, paclitaxel and L-ascorbic acid. These compounds are identified for the first time as hOat2 substrates. A wide range of structurally unrelated organic compounds inhibited the hOat2-mediated uptake of tetracycline, except for sulfobromophthalein. All of these findings indicate that hOat2 is a sodium-independent multi-specific organic anion/dimethyldicarboxylate exchanger. Our present findings thus provide further insights into the role of hOat2 in hepatic drug transport.

Animals↗
PubMed1980

Hydroxymethylglutaryl CoA lyase deficiency: features resembling Reye syndrome.

A 2-year-old boy had acute fever, malaise, and somnolence with hepatomegaly, increased blood ammonia content (338 microM), high SGOT, low blood glucose content, and mild acidosis. A liver biopsy showed diffuse accumulation of lipid droplets in swollen hepatocytes, and abnormal urinary metabolites included beta-hydroxy-beta-methyl glutarate (HMG), beta-methylglutaconate, beta-hydroxyisovalerate, and beta-methylglutaric and glutaric acids. In cultured skin fibroblasts and liver, beta-hydroxy-beta-methyl glutaryl CoA lyase activity was about 10% of normal. Therefore, a genetic deficiency of HMGCoA lyase activity can cause a clinical syndrome similar to that of Reye syndrome when the patient is stressed by an acute viral infection.

Amino Acids↗
PubMed2007

Role of mouse organic anion transporter 3 (mOat3) as a basolateral prostaglandin E2 transport pathway.

Renal organic anion transporters play an important role in the handling of a number of endogenous and exogenous anionic substances in the kidney. In this study, we investigated prostaglandin E(2) (PGE(2)) transport properties and intrarenal localization of mouse organic anion transporter 3 (mOat3). When expressed in Xenopus oocytes, mOat3 mediated the time- and concentration-dependent transport of PGE(2) (K(m): 1.48 microM). PGE(2) transport mediated by mOat3 was trans-stimulated by intracellular glutarate injected into the oocytes. PGE(2) efflux via mOat3 was also trans-stimulated by extracellular glutarate. Thus, mOat3 was shown to mediate the bidirectional transport of PGE(2), partly coupled to the dicarboxylate exchange mechanism. Immunohistochemical study revealed that mOat3 protein was localized at the basolateral membrane of renal proximal and distal tubules. Furthermore, diffuse expression of mOat3, including expression in the basolateral membrane in macula densa (MD) cells, was observed. These results indicate that mOat3 plays an important role as a basolateral transport pathway of PGE(2) in the distal nephron including MD cells that may constitute one of the indispensable steps for renin release and regulation of the tubuloglomerular feedback mechanism.

Animals↗
PubMed2001

Measurement of pancreatic lipase activity in serum by a kinetic colorimetric assay using a new chromogenic substrate.

We evaluate a new assay reagent for lipase determination, based on the use of 1,2-o-dilauryl-rac-glycero-3-glutaric acid-(6'-methylresorufin) ester (DGGR) as substrate. DGGR is cleaved by lipase, resulting in an unstable dicarbonic acid ester which is spontaneously hydrolysed to yield glutaric acid and methylresorufin, a bluish-purple chromophore with peak absorption at 580 nm. The rate of methylresorufin formation is directly proportional to the lipase activity in the sample. Bile salts, colipase and calcium chloride are included to provide optimal reactivity and specificity. Analysis of total imprecision gave a coefficient of variation of between 5.7% and 9.6%. Anticoagulants, common interfering substances and carboxylesterase had no effect on the assay, but interference by increased concentrations of serum triglycerides was noted. Good correlations were obtained with turbidimetry and a coupled enzymatic method. The estimated reference interval was 6-38 U/L. The unique characteristics of the chromogenic substrate qualify the present method as an innovative approach to serum lipase analysis.

Anticoagulants↗
PubMed2007

Human renal organic anion transporter 4 operates as an asymmetric urate transporter.

Human organic anion transporter 4 (hOAT4) is located at the apical membrane of proximal tubule cells and involved in renal secretion and reabsorption of endogenous substances as well as many drugs and xenobiotics. This study reevaluated the physiologic role, transport mode, and driving forces of hOAT4. 6-Carboxyfluorescein (6-CF) uptake into HEK293 cells that stably expressed hOAT4 was saturable, resulting in a K(m) of 108 muM. 6-CF as well as [(3)H]estrone sulfate ([(3)H]ES) accumulation by HEK293-hOAT4 cells were abolished by ES, dehydroepiandrosterone sulfate, sulfinpyrazone, benzbromarone, and probenecid, whereas several OA, including p-aminohippurate (PAH), lactate, pyrazinoate, nicotinate, glutarate, and the diuretic hydrochlorothiazide (HCTZ) exhibited a slight or a NS inhibitory effect. PAH and glutarate are not taken up by HEK293-hOAT4 cells, but they trans-stimulated 6-CF and [(3)H]ES uptake, indicating an asymmetric interaction of hOAT4 with these substrates. In chloride-free medium, HEK293-hOAT4-mediated [(3)H]PAH efflux was almost abolished, whereas addition of ES restored it comparable to Ringer solution, consistent with a physiologic ES/PAH or PAH/Cl(-) exchange mode of hOAT4. Moreover, an acidification of the uptake medium increased 6-CF as well as [(3)H]ES uptake, which was reduced by nigericin, suggesting that hOAT4 also can operate as an OA/OH(-) exchanger. hOAT4 facilitates substantial uptake of [(14)C]urate, which was elevated 2.6-fold by intracellular HCTZ. Thus, hOAT4 is the long-postulated, low-affinity apical urate anion exchanger that facilitates HCTZ-associated hyperuricemia.

Animals↗
PubMed1993

Tissue concentration and urinary excretion pattern of sulfofluorescein by the rat kidney.

In order to find a fluorescein analog that is excreted in a way similar to p-aminohippurate (PAH) and is suitable to register excretion into the urine and also to monitor continuously the concentration within cortical tissue, the interference of fluorescein, sulfofluorescein (SF), and fluorescein-5(6)-sulfonate with the contraluminal transport systems of PAH, succinate, and sulfate and with the luminal transport system of sulfate and lactate was evaluated. All three substances exerted a strong inhibitory potency against contraluminal PAH uptake (apparent Ki, 0.06 to 0.1 mmol/L) and also showed a moderate to small inhibitory potency against contraluminal sulfate transport (apparent Ki, 0.7 to 5.3 mmol/L). None of the three substrates interacted with the contraluminal dicarboxylate transport. Luminally, fluorescein and SF interacted with the lactate transporter (apparent Ki, approximately 3.0 mmol/L), whereas SF and fluorescein-5(6)-sulfonate had a very weak inhibitory potency against luminal sulfate transport (apparent Ki, 30 to 40 mmol/L). Because of its relatively low interference with the contraluminal sulfate transport, we preferred SF in the following study (protein binding, 88%) over fluorescein-5(6)-sulfonate (protein binding, 43.3%) and fluorescein (protein binding, 77.3%). A bolus injection of SF was given together with [14C]inulin into the jugular vein to rats in mannitol diuresis. Excretion of both substances in the urine was measured in 5-min samples. Fluorescence of the kidney surface was monitored at the exposed kidney with a photocell (excitation light, 470 nm; emission light, 530 nm). The effect of interfering substances was evaluated by their application 1 min before, simultaneously, or 1 min after SF bolus injection. PAH < probenecid < apalcillin inhibited SF excretion in the urine and, to a similar degree, SF fluorescence in cortical tissue. Inhibition was strongest when the substances were given simultaneously with SF. With the injection of alpha-ketoglutarate, glutarate, and succinate, an increase of SF excretion in the urine and, partially also, of SF content in tissue was seen. Tetrafluorosuccinate and mercaptosuccinate inhibited urinary SF excretion and tissue fluorescence strongly. Therefore, SF secretion is completely inhibited whereas filtration remained unaffected. The injection of acetate, lactate, and pyruvate as well as of 2-chloropropionate and thiosulfate did not change urinary excretion and tissue fluorescence of SF significantly. In SF-preloaded animals, the injection of probenecid, apalcillin, tetrafluorosuccinate, and mercaptosuccinate caused an immediate decrease of cellular SF content, whereas the injection of glutarate caused an increase. SF fluorescence in tissue was linearly related to urinary excretion of SF, whereas urinary excretion of inulin was barely affected.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1996

The formation of a crosslinked carboxyhemoglobin membrane at an organic-aqueous interface.

A 30% carboxyhemoglobin solution was encapsulated with a membrane composed of crosslinked hemoglobin as a potential artificial red blood cell by adding a 25 microL droplet of 30% carboxyhemoglobin solution in phosphate buffer to a buffer-saturated toluene solution of a homobifunctional crosslinking agent. Disuccinimidyl glutarate, disuccinimidyl suberate, and terephthaldicarboxaldehyde proved successful in crosslinking hemoglobin at concentrations of 0.05%, 0.08%, and 4.3%, respectively (saturated levels in buffer-saturated toluene). Disuccinimidyl glutarate exhibited maximal crosslinking of 11.0% in approximately 30 minutes. Disuccinimidyl suberate and terephthaldicarboxaldehyde required at least 12 hours to form a viable sphere and crosslinked 39.4% and 37.8% of the hemoglobin in 18 hours. Membrane integrity was assessed by determining the permeability of uncrosslinked hemoglobin through the membrane as a function of time.

Carboxyhemoglobin↗
PubMedDate not supplied

[Modification of the carboxyl and amine groups of the cellulolytic enzymes of Aspergillus awamori].

The activity and stability of some enzymes of Asp. awamori cellulolytic complex were studied as affected by chemical modification of carboxylic groups with N,N'-dicyclohexyl carbodiimide (DCCD) and amine groups with glutaric aldehyde. The carboxylic groups are established to be necessary for manifestation of the activities of C1- and C2-cellulases, Cx-exo- and Cx-endoglucanases. Their role is negligible in the action of beta-glucosidase. The activity of individual cellulases was studied as affected by nucleophilic substitution of DCCD-activated COOH-groups by various reagents (glycine amide, leucine amide, tyrosine amide and N-benzoyl-l-arginine-methyl ether-hydrochloride). Tyrosine amide is the least inacting reagent for all the enzymes, glycine amide is somewhat more activating. Essential differences are shown in the chemical and catalytic properties of Cx-exoglucanase and beta-glucosidase. It is found (under the effect of glutaric aldehyde) that amino groups are significant for manifestation of the activities of C1- and C2-cellulases and Cx-endoglucanase and to a less extent for that of Cs-exoglucanase and beta-glucosidase. It is supposed that electrostatic interactions of the carbolytic and amine groups might be an essential factor for stability of C1- and C2-cellulases and Cx-endoglucanase.

Amines↗