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PubMed1996

Axial distribution of band 3-positive intercalated cells in the collecting duct of control and ammonium chloride-loaded rabbits.

Recent studies have suggested that less than 10% of intercalated cells in the rabbit outer cortical collecting duct (CCD) [1, 2] and less than 3% in the connecting segment (CNT) [3] are identifiable by functional criteria as acid-secreting (type A or alpha) intercalated cells. Other studies, using peanut lectin-binding and the absence of apical endocytic activity to identify bicarbonate-secreting (type B or beta) intercalated cells, have suggested that acid-loading increases the percentage of alpha intercalated cells in the CCD. Because our preliminary observations of band 3 immunoreactivity suggest that the percentages of alpha intercalated cells in the rabbit outer CCD and the CNT are underestimated by physiologic studies and are not altered by chronic acid-loading, we quantified the percentage of alpha intercalated cells in various segments of the collecting duct using light microscopic immunohistochemistry in kidneys of rabbits receiving tap water (control) or 75 mM NH4Cl for 12 days plus 8 daily gavages of 2 to 6 mEq NH4Cl/kg body wt. Mean urine pH values were 5.96 in acid-loaded animals versus 8.47 in controls. Kidneys were preserved by in vivo perfusion with periodatelysine-paraformaldehyde fixation and processed for immunohistochemical colocalization using sequential labeling with monoclonal antibodies and peanut lectin, followed by immunoperoxidase detection. Colocalization of band 3 and carbonic anhydrase II immunoreactivity revealed the following percentages of band 3-positive intercalated cells in control versus NH4Cl rabbits: CNT, 49.0 versus 52.8; initial collecting tubule (ICT), 27.2 versus 34.5; outer CCD, 33.5 versus 30.3; inner CCD, 38.2 versus 41.8; corticomedullary CD, 67.9 versus 58.8. There were no differences between the groups for all comparisons. Similar results were obtained using band 3 protein immunoreactivity and peanut lectin-binding to identify intercalated cell subtypes. However, in NH4Cl-loaded rabbits, peanut lectin-binding was observed in band 3 positive intercalated cells in the outer medullary CD. We conclude that: (1) the percentage of alpha intercalated cells in rabbit CCD subsegments are approximately 50% in the CNT, 30% in the ICT and the outer CCD, 40% in the inner CCD, and 60% in the corticomedullary CD; (2) the percentage of alpha intercalated cells is not altered by chronic NH4Cl-loading; (3) peanut lectin is not a specific marker of beta intercalated cells.

Ammonium Chloride↗

PubMed2006

Chemo-enzymatic synthesis of raffinose-branched polyelectrolytes and self-assembly application in microcapsules.

A novel biocompatible polyelectrolyte poly(vinyl raffinose-co-acrylic acid) (PRCA) containing a raffinose branch was prepared via redox polymerization using Fe(2+)/K(2)S(2)O(8)/H(2)O(2) starting from enzymatically-synthesized monomer: 1-O-vinyldecanedioyl raffinose. Copolymers with different monomer feed ratios were prepared and characterized with IR, NMR, and GPC. PRCA can be alternated with polycation to form microcapsules on a crystals template by electrostatic layer-by-layer technique. The multilayers of PRCA/poly(methacryloyloxyethyl dimethylbenzyl ammonium chloride) (PMBA) on quartz slides and PRCA/poly(dimethyldiallyl ammonium chloride) (PDDA) on acyclovir crystals template were fabricated and characterized with UV-Vis spectra, the microelectrophoretic measurement, and TEM. Hollow capsules can be formed after the removal of acyclovir crystals template in a buffer solution. The nano-capsule-carrying galactose residue is a potential targeting drug-controlled delivery systems.

Acrylates↗

PubMed1986

Purification of ricin A1, A2, and B chains and characterization of their toxicity.

This paper describes a protocol for the preparation of highly purified A (A1 and A2) and B chains of the plant toxin, ricin, and biochemical and biological characterization of these proteins. Intact ricin was bound to acid-treated Sepharose 4B and was split on the column into A and B chains with 2-mercaptoethanol. The A chains were eluted with borate buffer containing 2-mercaptoethanol. A1 and A2 were then partially separated by cation exchange chromatography and the contaminating B chain was removed by affinity chromatography on Sepharose-asialofetuin and Sepharose-monoclonal anti-B chain. The B chain was eluted from the Sepharose 4B column by treatment with galactose and was further purified by cation and anion exchange chromatography; contaminating A chains were removed by affinity chromatography on Sepharose-monoclonal anti-A chain. The purified A and B chains were active as determined by their ability to inhibit protein synthesis in a cell-free assay and their binding to asialofetuin, respectively. Furthermore, by polyacrylamide gel electrophoresis, toxicity in mice, and toxicity on several different cell types, both A and B chains were shown to be minimally cross-contaminated. Finally, it was shown that ammonium chloride significantly enhanced the nonspecific toxicity of B chains for cells in vitro. In contrast, ammonium chloride did not enhance either the nonspecific toxicity of A chains in vitro or the specific toxicity of A chain-containing immunotoxins prepared with the highly purified A1, A2 chains.

Ammonium Chloride↗

PubMed1995

Purification and properties of glutamine synthetase from Nocardia asteroides.

Glutamine synthetase (GS, EC 6.3.1.2) from Nocardia asteroides was purified to homogeneity by ammonium sulfate precipitation, Sephadex G-150, and DEAE-Sepharose chromatography. The native molecular weight of the purified enzyme was determined to be 720 kDa. SDS-PAGE analysis of the purified preparation revealed a single band corresponding to 59 kDa, indicating the possible presence of 12 identical subunits. The divalent cations Mn2+ and Mg2+ were found to be essential for optimal transferase and biosynthetic activity, respectively. The optimal pH and temperature for both activities of the enzyme were found to be 7.2 and 50 degrees C. Amino acids such as L-alanine, glycine, and aspartate inhibited the GS activity. The Km values for the substrates of the biosynthetic reaction ATP, glutamate, and ammonium chloride were found to be 400 microM, 7.7 mM, and 200 microM, respectively. Addition of ammonium chloride to the nitrogen-limited culture resulted in a decrease of GS transferase and biosynthetic activities. Phosphodiesterase treatment of the extract from ammonia-shocked cultures showed an increase in GS transferase activity. The results indicate the possible regulation of GS by covalent modification.

Amino Acids↗

PubMed1999

Acidosis-induced coronary constriction in the rat heart: evidence for the activation of L-type calcium channels.

Perfused rat hearts were used to study the effects of acidosis on coronary tone. When pH was decreased, over the range pH 7.4 to pH 6.2, by reducing perfusate bicarbonate levels, under constant flow conditions, there was a transient decrease in coronary perfusion pressure (CPP), followed by a sustained acidosis-dependent increase in CPP, which reversed when pH was returned to pH 7.4. This increase in CPP was seen at perfusion rates of 5, 10, and 20 ml/min(-1). When using constant pressure perfusion acidosis reduced coronary flow. In a HEPES-buffered bicarbonate-free solution, acidosis did not cause a transient fall in CPP but it did produce a sustained increase in CPP. Addition of ammonium chloride (10 mM) reduced CPP, while washout of ammonium chloride increased CPP. The acidosis-induced increase in CPP was not affected by indomethacin, nitro-L-arginine, the nonselective adenosine receptor antagonist, 8-phenyl theophylline, or the thromboxane receptor antagonist, ZD 1542. The acidosis-induced increase in CPP was independent of the myocardial depressant effects of acidosis, but was attenuated by three different L-type calcium channel blockers. These results demonstrate that the coronary circulation of the rat constricts in response to acidosis. Experiments performed with L-type calcium channel blockers, and the calcium channel activator BAY K8644, suggest that constriction occurs via activation of L-type calcium channels. This would not be expected on the basis of electrophysiological studies, which have shown an inhibition of L-type calcium channels by acidosis.

Acidosis↗

PubMed2000

Evidence of relaxant effect of omeprazole in rabbit corpus cavernosum in vitro.

The present experiments were designed to investigate the effects of omeprazole, a H(+)-K+ ATPase inhibitor, on corporal smooth muscle tone in vitro. All spontaneous contractile activity in the corpus cavernosum was blocked following omeprazole (0.1 mM-1 mM) administration. However atropine (1 microM), Nw-nitro L-arginine methyl ester (L-NAME, 30 microM) or indomethacin (10 microM) did not affect the spontaneous contraction. Omeprazole (10 microM-1 mM) concentration-dependently induced relaxation in corporal smooth muscle precontracted with 10 microM phenylephrine or 80 mM KCl. Pretreatment of corporal tissue with L-NAME (30 microM), indomethacin (10 microM), ammonium chloride (7.5 mM), sodium acetate (7.5 mM), tetraethyl ammonium chloride (0.5 mM) or glibenclamide (1 microM) had no effect on the omeprazole induced relaxant responses. Nimodipine, an L-type Ca++ channel blocker, relaxed corporal strips precontracted with 80 mM KCl. Collectively, these results indicate that the inhibition of spontaneous contraction and the relaxation of precontracted corporal smooth muscle by omeprazole is probably mediated by the blockade of calcium channels. Further work is needed to determine the cellular mechanism(s) of action by which omeprazole acts on corpus cavernosum smooth muscle.

Animals↗

PubMed1983

1H-2-benzopyran-1-one derivatives, microbial products with pharmacological activity. Relationship between structure and activity in 6-[[1(S)-(3(S),4- dihydro-8-hydroxy-1-oxo-1H-2-benzopyran-3-yl)-3-methylbutyl]-amino]-4(S), 5(S)-dihydroxy-6-oxo-3(S)-ammoniohexanoate.

In order to investigate the structural requirements for gastroprotective activity in 6-[[1(S)-(3(S),4-dihydro-8- hydroxy-1-oxo-1H-2-benzopyran-3-yl)-3-methylbutyl]amino]-4(S),5(S)-dihydroxy 6-oxo-3(S)-ammoniohexanoate [AI-77-B, 1], a product of Bacillus pumilus AI-77, nine derivatives were prepared and then tested for protective activity against stress-induced ulcers in rats. Neither the chromophore, [1-(3,4-dihydro-8-hydroxy-1-oxo-1H-2-benzopyran-3-yl)-3-methylbutyl]ammonium chloride (2), nor the side-chain moiety, 4-amino-2,3-dihydroxyhexanedioic acid (4), as separate fragments alone showed any significant activity. Hydrolysis of the lactone ring of the 1H-2-benzopyran-1-one skeleton, to give 6-[[1-(2-carboxy-3-hydroxyphenyl)-2-hydroxy-5-methylhex-3-yl]amino]-4, 5-dihydroxy-6-oxo-3-ammoniohexanoate (5), led to a considerable decrease in activity. The formation of a gamma-lactone ring in the side chain, 4-[1-hydroxy-2-[[1-(3,4-dihydro-8-hydroxy-1-oxo-1H-2-benzopyran-3-yl) -3-methylbutyl]-amino]-2-oxoethyl]butan-4-olid-3-yl]ammonium chloride (6), resulted in a small decrease in activity. Selective acetylation at the primary amine position of 6, to give 4-[1-hydroxy-2- [[1-(3,4-dihydro-8- hydroxy-1-oxo-1H-2-benzopyran-3-yl)-3-methylbutyl]amino]-2-oxoethyl]-3- (acetylamino)butan-4-olide (7), led to a considerable decrease in activity. Both di- and triacetylated derivatives of 6, 4-[1-acetoxy-2 -[[1-(3,4-dihydro-8-hydroxy-1-oxo-1H-2-benzopyran-3-yl)-3-methylbutyl] amino]-2-oxoethyl]-3-(acetylamino)butan-4-olide (8) and 4-[1-acetoxy-2- [[1-(3,4- dihydro-8-acetoxy-1-oxo-1H-2-benzopyran-3-yl)-3-methylbutyl]amino]-2- oxoethyl]-3-(acetylamino)butan-4-olide (9), were inactive. Selective methylation of the phenolic hydroxyl group of to give 1, 6-[[1-(3,4-dihydro-8-methoxy-1-oxo-1H-2-benzopyran-3-yl) -3-methylbutyl]amino]-4,5-dihydroxy-6-oxo-3-ammoniohexanoate (15), resulted in a small decrease in activity. On the other hand, conversion of the carboxyl group of the side chain to an amide, to give [6-[[1-(3,4-dihydro-8-hydroxy-1-oxo-1H-2-benzopyran-3-yl)- 3-methylbutyl]amino]-4,5-dihydroxy-6-oxo-3-hexanamido]ammonium chloride (10), caused a considerable increase in both activity and toxicity. The findings showed that modifications at the position of the amino acid moiety of 1 significantly influenced the activity and that the 1H-2-benzopyran-1-one skeleton was also required for activity to occur.

Animals↗

PubMedDate not supplied

Ammonium-mediated reduction of plasmid copy number and recombinant gene expression in Escherichia coli.

The effect of ammonium as a medium supplement on plasmid-encoded recombinant beta-galactosidase synthesis was explored in Escherichia coli cells during aerobic growth in complex medium. After induction, only doses of ammonium chloride below 1 g/L are able to transiently enhance the yield. However, the presence of nontoxic ammonium chloride concentrations of up to 10 g/L results in lower values of beta-galactosidase in a concentration-dependent fashion. A significant reduction in plasmid DNA content explains the decrease in the yield by a gene-dosage-involving mechanism.

Ammonium Chloride↗

PubMed1996

Uptake of duck hepatitis B virus into hepatocytes occurs by endocytosis but does not require passage of the virus through an acidic intracellular compartment.

The infectious entry pathway of duck hepatitis B virus (DHBV) was investigated with primary duck hepatocytes. Virus uptake was measured by a selective PCR technique which allows for the detection of a successful infection without the need for viral replication or gene expression. To test whether DHBV uptake occurs by endocytosis, the effects of energy depletion were analyzed. The requirement for an acidic intracellular pH was tested with the lysosomotropic agent ammonium chloride. The data show that energy depletion prevents the uptake of DHBV into primary hepatocytes whereas ammonium chloride has no effect. From these data, we conclude that DHBV is taken up by its host cells by endocytosis. However, in contrast to that of most other enveloped viruses, escape of DHBV from the endocytotic route does not depend on an acidic intracellular compartment.

Ammonium Chloride↗

PubMed2000

Study of urinary acidification in patients with idiopathic hypocitraturia.

Hypocitraturia (HCit) is one of the most remarkable features of renal tubular acidosis, but an acidification defect is not seen in the majority of hypocitraturic patients, whose disease is denoted idiopathic hypocitraturia. In order to assess the integrity of urinary acidification mechanisms in hypocitraturic idiopathic calcium stone formers, we studied two groups of patients, hypocitraturic (HCit, N = 21, 39.5 +/- 11.5 years, 11 females and 10 males) and normocitraturic (NCit, N = 23, 40.2 +/- 11.7 years, 16 females and 7 males) subjects, during a short ammonium chloride loading test lasting 8 h. During the baseline period HCit patients showed significantly higher levels of titratable acid (TA). After the administration of ammonium chloride, mean urinary pH (3rd to 8th hour) and TA and ammonium excretion did not differ significantly between groups. Conversely, during the first hour mean urinary pH was lower and TA and ammonium excretion was higher in HCit. The enhanced TA excretion by HCit during the baseline period and during the first hour suggests that the phosphate buffer mechanism is activated. The earlier response in ammonium excretion by HCit further supports other evidence that acidification mechanisms react promptly. The present results suggest that in the course of lithiasic disease, hypocitraturia coexists with subtle changes in the excretion of hydrogen ions in basal situations.

Acidosis, Renal Tubular↗

PubMed1978

Mechanism of the metabolic acidosis of selective mineralocorticoid deficiency.

The mechanism of generation of metabolic acidosis in selective mineralocorticoid deficiency was investigated in bilaterally adrenalectomized (ADX) rats treated with dexamethasone and in sham-operated (S) rats. ADX rats had significantly lower plasma sodium and bicarbonate concentrations and significantly higher plasma potassium concentrations than S rats did. ADX rats developed negative sodium balance when fed a "zero" sodium diet. The minimum urine pH achieved during sodium sulfate infusion and during ammonium chloride administration was not significantly different between ADX and S rats. Bicarbonate reabsorption and urine minus blood PCO2 gradient were not different between ADX and S rats. For any given urine pH, absolute ammonium excretion was significantly lower in ADX than it was in S rats, both during sodium sulfate infusion and during chronic ammonium chloride administration. Glomerular filtration rate (GFR) was significantly lower in ADX than it was in S rats; ammonium excretion corrected for GFR was not different between the two groups. To determine the role of decreased distal sodium delivery (secondary to decrease in GFR and enhanced proximal sodium reabsorption which resulted from distal sodium chloride wastage) on ammonium excretion, ADX rats were fed 0.9% sodium chloride in an effort to keep body weight constant. Salt-loaded ADX rats had a plasma bicarbonate concentration higher than did S rats. Salt-loading also led to a significant increase in GFR; absolute ammonium excretion was significantly higher than that of other ADX rats with the same degree of acidosis. At comparable levels of GFR, there was no difference in ammonium excretion between ADX and S rats. Ammonium excretion was linearly related to GFR. ADX rats fed a zero potassium diet had significantly greater ammonium excretion than did all other groups of ADX or S rats receiving a normal potassium intake. These data suggest that volume contraction is a major factor responsible for the acidosis of selective mineralocorticoid deficiency.

Acidosis↗

PubMed1999

Early acidification of phagosomes containing Brucella suis is essential for intracellular survival in murine macrophages.

Brucella suis is a facultative intracellular pathogen of mammals, residing in macrophage vacuoles. In this work, we studied the phagosomal environment of these bacteria in order to better understand the mechanisms allowing survival and multiplication of B. suis. Intraphagosomal pH in murine J774 cells was determined by measuring the fluorescence intensity of opsonized, carboxyfluorescein-rhodamine- and Oregon Green 488-rhodamine-labeled bacteria. Compartments containing live B. suis acidified to a pH of about 4.0 to 4.5 within 60 min. Acidification of B. suis-containing phagosomes in the early phase of infection was abolished by treatment of host cells with 100 nM bafilomycin A(1), a specific inhibitor of vacuolar proton-ATPases. This neutralization at 1 h postinfection resulted in a 2- to 34-fold reduction of opsonized and nonopsonized viable intracellular bacteria at 4 and 6 h postinfection, respectively. Ammonium chloride and monensin, other pH-neutralizing reagents, led to comparable loss of intracellular viability. Addition of ammonium chloride at 7 h after the beginning of infection, however, did not affect intracellular multiplication of B. suis, in contrast to treatment at 1 h postinfection, where bacteria were completely eradicated within 48 h. Thus, we conclude that phagosomes with B. suis acidify rapidly after infection, and that this early acidification is essential for replication of the bacteria within the macrophage.

Ammonium Chloride↗

PubMed1992

The Murray Valley encephalitis virus prM protein confers acid resistance to virus particles and alters the expression of epitopes within the R2 domain of E glycoprotein.

To study the role of the precursor to the membrane protein (prM) in flavivirus maturation, we inhibited the proteolytic processing of the Murray Valley encephalitis (MVE) virus prM to membrane protein in infected cells by adding the acidotropic agent ammonium chloride late in the virus replication cycle. Viruses purified from supernatants of ammonium chloride-treated cells contained prM protein and were unable to fuse C6/36 mosquito cells from without. When ammonium chloride was removed from the cells, both the processing of prM and the fusion activity of the purified viruses were partially restored. By using monoclonal antibodies (MAbs) specific for the envelope (E) glycoprotein of MVE virus, we found that at least three epitopes were less accessible to their corresponding antibodies in the prM-containing MVE virus particles. Amino-terminal sequencing of proteolytic fragments of the E protein which were reactive with sequence-specific peptide antisera or MAb enabled us to estimate the site of the E protein interacting with the prM to be within amino acids 200 to 327. Since prM-containing viruses were up to 400-fold more resistant to a low pH environment, we conclude that the E-prM interaction might be necessary to protect the E protein from irreversible conformational changes caused by maturation into the acidic vesicles of the exocytic pathway.

Acids↗

PubMed1963

Liver disease and ammonia intoxication.

The relation between ammonia intoxication and liver disease is not clear. Ammonia appears to be relatively non-toxic to normal individuals, whereas some patients with liver disease appear to be exquisitely sensitive to dietary protein, ammonia-releasing substances, and ammonium salts. In an attempt to elucidate this relationship the intravenous LD(50) of ammonium chloride was determined in both normal mice and in those with liver disease produced by a variety of means. Parenchymal damage was created by acute and chronic carbon tetrachloride intoxication, a low-protein, lipotrope-deficient diet, and mouse hepatitis virus. Mice in which the portal vein had been partially ligated and those infected with Schistosoma mansoni developed portal-systemic collateral circulation. Groups of these mice were placed on high-protein diets and ammonia drinking water for periods as long as two months. A combination of both parenchymal damage and collateral circulation was induced in mice either by bile duct ligation or by a combination of schistosomiasis and acute carbon tetrachloride intoxication. When the above groups of mice with liver disease were compared with normal control mice in the same weight range, the LD(50) of ammonium chloride showed no striking change.

Ammonia↗

PubMed2002

Role of glutamine and arginase in protection against ammonia-induced cell death in gastric epithelial cells.

Ammonia is a cytotoxic factor produced during Helicobacter pylori infection that may reduce the survival of surface epithelial cells. Here we examine whether ammonia kills cells and whether L-glutamine (L-Gln) protects against cell death by stimulating ammonia detoxification pathways. Cell viability and vacuolation were quantified in rat gastric epithelial (RGM1) cells incubated with ammonium chloride at pH 7.4 in the presence or absence of L-Gln. Incubation of RGM1 cells with ammonium chloride caused a dose-dependent increase in cell death and vacuolation, which were both inhibited by L-Gln. We show that RGM1 cells metabolize ammonia to urea via arginase, a process that is stimulated by L-Gln and results in reduced ammonia cytotoxicity. L-Gln also inhibits the uptake and facilitates the extrusion of ammonia from cells. Blockade of glutamine synthetase did not reduce the survival of RGM1 cells, demonstrating that the conversion of L-glutamate and ammonia to L-Gln is not involved in ammonia detoxification. Thus our data support a role for L-Gln and arginase in protection against ammonia-induced cell death in gastric epithelial cells.

Ammonia↗

PubMed1997

Reovirus variants selected during persistent infections of L cells contain mutations in the viral S1 and S4 genes and are altered in viral disassembly.

Reoviruses isolated from persistently infected cultures (PI viruses) can grow in the presence of ammonium chloride, a weak base that blocks acid-dependent proteolysis of viral outer-capsid proteins during viral entry into cells. We used reassortant viruses isolated from crosses of wild-type (wt) reovirus strain, type 1 Lang, and three independent PI viruses, L/C, PI 2A1, and PI 3-1, to identify viral genes that segregate with the capacity of PI viruses to grow in cells treated with ammonium chloride. Growth of reassortant viruses in ammonium chloride-treated cells segregated with the S1 gene of L/C and the S4 gene of PI 2A1 and PI 3-1. The S1 gene encodes viral attachment protein sigma1, and the S4 gene encodes outer-capsid protein sigma3. To identify mutations in sigma3 selected during persistent reovirus infection, we determined the S4 gene nucleotide sequences of L/C, PI 2A1, PI 3-1, and four additional PI viruses. The deduced amino acid sequences of sigma3 protein of six of these PI viruses contained a tyrosine-to-histidine substitution at residue 354. To determine whether mutations selected during persistent infection alter cleavage of the viral outer capsid, the fate of viral structural proteins was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after treatment of virions of wt and PI viruses with chymotrypsin in vitro. Proteolysis of PI virus outer-capsid proteins sigma3 and mu1C occurred with faster kinetics than proteolysis of wt virus outer-capsid proteins. These results demonstrate that mutations in either the S1 or S4 gene alter acid-dependent disassembly of the reovirus outer capsid and suggest that increased efficiency of proteolysis of viral outer-capsid proteins is important for maintenance of persistent reovirus infections of cultured cells.

Animals↗

PubMed1988

Superoxide production in aprotic interior of chloroplast thylakoids.

The site of superoxide production in spinach thylakoids was found to be the aprotic interior of the thylakoid membranes near the P700 chlorophyll a protein at the reaction center of photosystem I complexes. This conclusion was drawn from the following findings. (i) Cytochrome c reduction by illuminated thylakoids, which was confirmed to be superoxide dependent by the failure of this reaction to occur in anaerobiosis, was completely inhibited by a dibutyl catechol, but partially inhibited by a hydrophilic disulfonated derivative. (ii) P700 chlorophyll a proteins were preferentially iodinated by lactoperoxidase by the use of hydrogen peroxide that was derived from the disproportionation of superoxides in illuminated thylakoids. (iii) Hydrogen peroxide production and oxygen uptake were induced by ammonium chloride, a proton conductor that can permeate through thylakoid membranes, but whole superoxide in the bulk solution was oxidized back to molecular oxygen by cytochrome c. The effective concentration of ammonium chloride decreased to one-sixtieth of the original, when an ammonium ion ionophore, nonactin, was added. Thus, the weak acid allowed superoxide to yield hydrogen peroxide disproportionately in the thylakoid membrane interior.

Ammonium Chloride↗

PubMed1980

Changes in renal metabolite profile and ammoniagenesis during acute and chronic metabolic acidosis in dog and rat.

Acute metabolic acidosis was induced by an i.v. administration of hydrochloric acid to dogs and rats to decrease the plasma bicarbonate concentration from 22 to 12 mM in dogs and from 26 to 10 mM in rats. Chronic metabolic acidosis was also induced in dogs by ammonium chloride feeding for 5 days. Rats also were given ammonium chloride for 24 hours. The renal metabolite profile was determined on the freeze-clamped renal tissue before and after 100 min (dogs) or 30 to 240 min (rats) of acsute acidosis. Measurements on chronically acidotic dogs and rats with 24-hour acidosis were obtained also for comparison with acute acidosis. In both species, kidney glutamine, glutamate, and alpha-ketokglutarate concentrations decreased drastically following induction of acute or chronic acidosis, In the dog, or in the rat during the first 2 hours of acidosis, malate concentration was unchanged. Malate concentration fell significantly in the rat kidney only after 2 hours of acidosis without change in phosphoenolpyruvate (PEP) concentration. In chronically acidotic dogs, malate and oxaloacetate rose fivefold with no change in PEP concentration. Phosphoenolpyruvate carboxykinase (PEPCK) activity was not stimulated by chronic metabolic acidosis in the dog in contrast to the rat. Acute acidosis by hydrochloric acid increased net renal glutamine extraction in the rat but not in the dog. These data suggest that an increased metabolic flux occurs between alpha-ketoglutarate and malate in both rat and dog kidney during acute metabolic acidosis. In the rat, however, after 2 hours, PEPCK activation modifies the kidney metabolite profile. Intrarenal glutamine transport seems to be a rate-limiting factor for adaptation to acute acidosis in the dog but not in the rat kidney.

Acidosis↗