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PubMed1996

[Nitrite formation and nitrosation potential of heterotrophic biological denitrification of drinking water in laboratory conditions].

In a laboratory construction for heterotrophic biological denitrification of drinking water treatment, the formation of nitrite, the potency of nitrosation and the genotoxic activity were tested. Parameter as nitrate concentration, the water flow rate in the system, nitrite and morpholine addition and the pH-value were checked. For testing the potency of nitrosation and formation of nitrite in the reactor we took morpholine, a fast nitrosing amine. The results show for the break down rate of nitrate, there is no influence of the initial nitrate concentration (80-195 mg/L), the nitrite addition (5-20 mg/L) and the water flow rate (45-100 min) in the system. pH-values below 5.5 showed a little break down rate of nitrate. There was no correlation between the starting point of nitrate concentration and the formation of nitrite, although there was a positive correlation between the length of stay and the formation of nitrite. Nitrite concentrations of 5 mg/L with morpholine concentrations of 5 and 10 mg/L didn't show detectable formation of nitrosomorpholine. The analyses of different watertests in the construction didn't show significant results for DNA damage by the sister-chromatid exchange (SCE). The results of the Salmonella microsome assay (tester strain TA1535) didn't show any mutagenic effects relating to the potency of nitrosation. According to our experiments the potency of generalising nitrosamides or nitrosamines by drinking water denitrification seems to be low. There is no final assessment of detriment to health by denitrifying drinking water.

Animals↗

PubMed1997

Nitrite plasma levels in acute and chronic coronary heart disease.

BACKGROUND: The authors carried out a study on the plasmatic levels of nitrites, which are the sole stable metabolites of nitric oxide (NO), in a group of subjects suffering from various clinical forms of coronary artery disease, aimed at evaluating the endothelial production of NO in acute and chronic ischemic conditions. METHODS: Our series consisted of 104 female subjects (mean age 65 +/- 5) subdivided into: a) 10 subjects with acute coronary heart disease (myocardial infarction); b) 32 with chronic non hypertensive coronary heart disease (CHD); c) 30 with hypertensive CHD (arterial blood pressure over 160/95 mmHg); d) 32 with CHD and hypercholesterolemia (values over 250 mg/dl). Thirty-seven female subjects (mean age 58 +/- 7) without internistic diseases were considered as control subjects. For each sample the plasmatic levels of nitrites were determined by the Gutman and Hollywood method. RESULTS: We discovered that in the patients with chronic coronary heart disease (CHD) the mean value of nitrites was 18 +/- 0.3 mumol/L, not significantly different from the controls (17 +/- 0.5 mumol/L). In the patients with acute CHD the nitrite plasma level were significantly (p < 0.05) higher (30 +/- 2.2 mumol/L) compared to the controls and the patients with chronic CHD. In the group of patients with hypertensive CHD the mean nitrite value was 20 +/- 0.6 mumol/L, significantly (p < 0.05) higher in comparison with the group of non-hypertensive CHD patients (14 +/- 0.3 mumol/L). In the subjects with CHD and hypercholesterolemia the mean value of nitrites was sharply elevated, (25 +/- 1.0 mumol/L), with a highly significant difference (p < 0.01) as compared to the normolipemic CHD patients. CONCLUSIONS: These results lead to the hypothesis that: strong NO production may play a compensatory and protective role during acute myocardial hypoxia; NO defective synthesis may depend on an exhaustive endothelial adjustment in subjects with long-term CHD; a significant increase of the relaxing factor in hypertensive conditions exists; a highly enhanced synthesis of the plasmatic nitrites in hypercholesterolemic patients means an engagement of NO to neutralize the endothelium-damaging molecular substances and particularly the oxided LDL.

Acute Disease↗

PubMed1998

Nitrite plasma levels in type 1 and 2 diabetics with and without complications.

BACKGROUND: The authors thought it interesting to examine the interrelationship between nitric oxide and diabetes mellitus by the determination of the nitrite plasma levels, stable end-products of nitric oxide, in various clinical patterns of diabetes mellitus. METHODS: Our series consisted of 161 female subjects (mean age 54 +/- 7 years, disease duration 5 +/- 3 months) subdivided into: a) 13 patients suffering from insulin-dependent diabetes (IDDM) without clinical and instrumental signs of micro- and macro-angiopathy; b) 148 suffering from non insulin-dependent diabetes mellitus (NIDDM) of whom: 1) 52 without vascular complications (28 normal weight, BMI < 25, and 24 obese, BMI > 30); 2) 40 with clinical and instrumental signs of non hypertensive coronary heart disease (CHD); 3) 25 with CHD and hypertension (arterial blood pressure over 160/95 mmHg); 4) 31 with hypercholesterolemia (values over 250 mg/dl). All patients were examined in good glycometabolic conditions reached by oral hypoglycemiant (12 cases) or insulin (149 cases) treatment. As normal control 37 female subjects (mean age 48 +/- 7) without internistic diseases were considered. For each sample we determined the plasma levels of nitrites by the Gutman and Hollywood method. RESULTS: Almost similar nitrite plasma levels in IDDM (17 +/- 0.5 mumol/L) and normal controls (17 +/- 0.2 mumol/L) were found; in non complicated non obese NIDDM a not significantly elevated value (21 +/- 0.8 mumol/L) as compared with the IDDM and control group was found; the obese NIDDM patients showed a value (18 +/- 0.4 mumol/L) not significantly different in comparison with the non obese NIDDM group. In the NIDDM group with non hypertensive CHD) the nitrite values was almost similar (20 +/- 0.5 mumol/L) to the corresponding group without vascular complications. In the patients with CHD and hypertension the nitrite level was superimposable (20 +/- 0.7 mumol/L) on the one recorded in NIDDM patients without vascular complications and in those with CHD without hypertension. In NIDDM patients with hypercholesterolemia the mean nitrite value was sharply elevated (24 +/- 0.8 mumol/L); the difference between this group and those of non hypercholesterolemic, non obese, obese and CHD (with or without hypertension) patients was significant (p < 0.05). CONCLUSIONS: It is conceivable that diabetes mellitus per se causes a tendential not significant increase of NO production in comparison with normal controls; some factors such as blood pressure, overweight, disease duration, therapeutic treatment and coronary complications appear not to influence NO production. In hypercholesterolemic diabetic patients the nitrite enhanced level in plasma might mean a compensatory response to a continuous inactivation of NO involved in a protective competition towards damaging factors and chiefly against oxidised LDL.

Adult↗

PubMed1998

Isolation and immunocytochemical location of the nitrite-oxidizing system in nitrospira moscoviensis

A membrane-associated nitrite-oxidizing system of Nitrospira moscoviensis was isolated from heat-treated membranes. The four major proteins of the enzyme fraction had apparent molecular masses of 130, 62, 46, and 29 kDa, respectively. The nitrite-oxidizing activity was dependent on the presence of molybdenum. In contrast to the nitrite oxidoreductase of Nitrobacter hamburgensis X14, the activity of the nitrite-oxidizing system of Ns. moscoviensis increased when solubilized by heat treatment. Electron microscopy of the purified enzyme revealed uniform particles with a size of approximately 7 x 9 nm. SDS-immunoblotting analysis of crude extracts showed that the monoclonal antibodies Hyb 153-3, which recognize the beta-subunit of the nitrite oxidoreductase from Nitrobacter, reacted with a protein of 50 kDa in Ns. moscoviensis. This protein corresponded to the protein of 46 kDa of the purified enzyme and contained a b-type cytochrome. Using electron microscopic immunocytochemistry and the monoclonal antibodies Hyb 153-3, the nitrite-oxidizing system of Ns. moscoviensis was shown to be located in the periplasmic space. Here a periodic arrangement of membrane-associated particles was found on the outside of the cytoplasmic membrane in the form of a hexagonal pattern. It is supposed that these particles represent the nitrite-oxidizing system in Nitrospira.

Journal Article↗

PubMed2005

Chemical conversion of nitrate and nitrite to nitrous oxide for nitrogen and oxygen isotopic analysis in freshwater and seawater.

We present a novel method for nitrogen and oxygen natural isotopic abundance analysis of nitrate and nitrite of seawater and freshwater at environmental concentrations. The method involves the reduction of nitrate to nitrite using spongy cadmium with further reduction to nitrous oxide using sodium azide in an acetic acid buffer. For separate nitrite analysis, the cadmium reduction step is simply bypassed. Nitrous oxide is purged from the water sample and trapped cryogenically using an automated system with subsequent release into a gas chromatography column. The isolated nitrous oxide is then analyzed on a continuous flow isotope ratio mass spectrometer via an open split. This paper describes the basic protocol and reaction conditions required to obtain reproducible natural abundance level nitrogen and oxygen isotopic ratios from nitrate, nitrite, or both, and the results obtained to support these conclusions. A standard deviation less than 0.2 per thousand for nitrogen and 0.5 per thousand for oxygen was found for nitrate samples ranging in concentration from 40 to 0.5 microM (better for nitrite), with a blank of 2 nmol for 50-mL samples. Nitrogen and oxygen isotopic fractionation and oxygen atom exchange were consistent within each batch of analysis. There was no interference from any seawater matrixes. Only one other method published to date can measure the nitrate oxygen isotopic abundance in seawater and none that do so for nitrite alone in the presence of nitrate. This method may prove to be simpler, faster, and obtain isotopic information for lower concentrations of nitrate and nitrite than other methods.

Journal Article↗

PubMed2001

The tetraheme cytochrome c NrfH is required to anchor the cytochrome c nitrite reductase (NrfA) in the membrane of Wolinella succinogenes.

The electron-transport chain that catalyzes nitrite respiration with formate in Wolinella succinogenes consists of formate dehydrogenase, menaquinone and the nitrite reductase complex. The latter catalyzes nitrite reduction by menaquinol and is made up of NrfA and NrfH, two c-type cytochromes. NrfA is the catalytic subunit; its crystal structure is known. NrfH belongs to the NapC/NirT family of membrane-bound c-type cytochromes and mediates electron transport between menaquinol and NrfA. It is demonstrated here by MALDI MS that four heme groups are attached to NrfH. A Delta nrfH deletion mutant of W. succinogenes was constructed by replacing the nrfH gene with a kanamycin-resistance gene cartridge. This mutant did not form the NrfA protein, probably because of a polar effect of the mutation on nrfA expression. The nrfHAIJ gene cluster was restored by integration of an nrfH-containing plasmid into the genome of the Delta nrfH mutant. The resulting strain had wild-type properties with respect to growth by nitrite respiration and nitrite reductase activity. A mutant (stopH) that contained the nrfHAIJ locus with nrfH modified by two artificial stop codons near its 5' end produced wild-type amounts of NrfA in the absence of the NrfH protein. NrfA was located exclusively in the soluble cell fraction of the stopH mutant, indicating that NrfH acts as the membrane anchor of the NrfHA complex in wild-type bacteria. The stopH mutant did not grow by nitrite respiration and did not catalyze nitrite reduction by formate, indicating that the electron transport is strictly dependent on NrfH. The NrfH protein seems to be an unusual member of the NapC/NirT family as it forms a stable complex with its redox partner protein NrfA.

Base Sequence↗

PubMed2002

The nrfI gene is essential for the attachment of the active site haem group of Wolinella succinogenes cytochrome c nitrite reductase.

The cytochrome c nitrite reductase complex (NrfHA) is the terminal enzyme in the electron transport chain catalysing nitrite respiration of Wolinella succinogenes. The catalytic subunit NrfA is a pentahaem cytochrome c containing an active site haem group which is covalently bound via the cysteine residues of a unique CWTCK motif. The lysine residue serves as the axial ligand of the haem iron. The other four haem groups of NrfA are bound by conventional haem-binding motifs (CXXCH). The nrfHAIJ locus was restored on the genome of the W. succinogenes DeltanrfAIJ deletion mutant by integration of a plasmid, thus enabling the expression of modified alleles of nrfA and nrfI. A mutant (K134H) was constructed which contained a nrfA gene encoding a CWTCH motif instead of CWTCK. NrfA of strain K134H was found to be synthesized with five bound haem groups, as judged by matrix-assisted laser-desorption/ionization (MALDI) mass spectrometry. Its nitrite reduction activity with reduced benzyl viologen was 40% of the wild-type activity. Ammonia was formed as the only product of nitrite reduction. The mutant did not grow by nitrite respiration and its electron transport activity from formate to nitrite was 5% of that of the wild-type strain. The predicted nrfI gene product is similar to proteins involved in system II cytochrome c biogenesis. A mutant of W. succinogenes (stopI) was constructed that contained a nrfHAIJ gene cluster with the nrfI codons 47 and 48 altered to stop codons. The NrfA protein of this mutant did not catalyse nitrite reduction and lacked the active site haem group, whereas the other four haem groups were present. Mutant (K134H/stopI) which contained the K134H modification in NrfA in addition to the inactivated nrfI gene had essentially the same properties as strain K134H. NrfA from strain K134H/stopI contained five haem groups. It is concluded that NrfI is involved in haem attachment to the CWTCK motif in NrfA but not to any of the CXXCH motifs. The nrfI gene is obviously dispensable for maturation of a modified NrfA protein containing a CWTCH motif instead of CWTCK. Therefore, NrfI might function as a specific haem lyase that recognizes the active site lysine residue of NrfA. A similar role has been proposed for NrfE, F and G of Escherichia coli, although these proteins share no overall sequence similarity to NrfI and belong to system I cytochrome c biogenesis, which differs fundamentally from system II.

Amino Acid Substitution↗

PubMed1996

Nitrite Transport in Chloroplast Inner Envelope Vesicles (I. Direct Measurement of Proton-Linked Transport).

Chloroplast inner envelope membrane vesicles that are loaded with the pH-sensitive fluorophore, pyranine, show rapid internal acidification when nitrite is added. Acidification is dependent upon [delta]pH, with the inside of vesicles being alkaline with respect to the outside. The rate of vesicle acidification was directly proportional to the concentration of nitrite that was added and the imposed pH difference across the membrane. In contrast, added nitrate had no effect on vesicle acidification. Nitrite also caused acidification of asolectin vesicles. The extent of vesicle acidification is dependent on the internal volume of vesicles. Inner envelope and asolectin vesicles that were prepared by extrusion were approximately the same size, allowing them to be compared when the final extent of acidification, measured after the pH gradient had collapsed, was similar. The rate of nitrite-dependent acidification was similar in these two preparations at any single nitrite concentration. These results indicate that nitrite movement occurs by rapid diffusion across membranes as nitrous acid, and this movement is dependent on a proton gradient across the lipid bilayer. Under conditions approximating those in vivo, the rate of diffusion of nitrous acid far exceeds that of nitrite reduction within chloroplasts.

Journal Article↗

PubMed1973

A Comparison of Nitrite Reductase Enzymes from Green Leaves, Scutella, and Roots of Corn (Zea mays L.).

Nitrite reductase from green leaves of corn (Zea mays L.) is eluted from a diethylaminoethyl-cellulose column in one peak of activity by a chloride gradient, while nitrite reductase from scutellum tissue is resolved into two peaks of activity, apparently representing two forms of the enzyme NiR1 and NiR2. One of these (NiR2) elutes at the same concentration of chloride as the leaf nitrite reductase. Roots and etiolated shoots also exhibited both forms of the enzyme, however, lesser amounts of NiR1 is extractable from these tissues than from scutellum. Comparison of green leaf nitrite reductase with NiR2 from scutellum tissue shows similar or identical properties with respect to molecular weight, isoelectric point, electron donor requirements, inhibition properties, pH optima, thermal stability, and pH tolerance. The significance of these similarities in relation to probable differences in the biochemical mechanism of nitrite reduction between leaf and scutellum tissues is discussed. Although ferredoxin is considered, with some reservations, to be the electron donor for nitrite reductase in green tissue, the reductant for nongreen tissue is not known. The possibility that nitrite reductases from green and non-green tissues uses the same electron donor, in vivo, is considered.

Journal Article↗

PubMed1976

Hydroxylamine reductase enzymes from maize scutellum and their relationship to nitrite reductase.

Three enzymes contribute to the total hydroxylamine reductase activity of corn (Zea mays L.) scutellum extracts. Two of these resemble enzymes previously prepared from leaves, while the third, which accounts for a major part of the activity, appears to have no counterpart in leaf tissue. One of the hydroxylamine reductases found only in small amounts is associated with nitrite reductase and is induced, together with nitrite reductase, by nitrite. The other two enzymes are noninducible by nitrite and can be totally separated from nitrite reductase, which subsequently remains capable of catalyzing the reduction of nitrite to ammonia. Possible causes of the decline of hydroxylamine reductase activity during the induction of nitrite reductase are discussed.

Journal Article↗

PubMed1979

Effects of certain herbicides and their combinations on nitrate and nitrite reduction.

A study was made concerning the effect of various herbicides, when used alone or in combination, on nitrite accumulation in excised leaves of wheat (Triticum aestivum L., var. ;Centurk'). Treatment of leaves with photosynthetic inhibitor herbicides, known to interfere with the transfer of light energy, caused accumulation of nitrite under illuminated, aerobic conditions. When certain other herbicides, which do not interfere with the photosynthetic process, were applied to leaves and incubated under dark, aerobic conditions, nitrite accumulations were enhanced over those treated with photosynthetic inhibitors or the controls. The combination of photosynthetic inhibitor herbicides and certain other "nonphotosynthetic inhibitor" herbicides caused relatively large amounts of nitrite to accumulate in light or in darkness. Nitrite accumulation occurs when nitrate and nitrite reduction are not in balance. The proposed actions of the herbicides used in this study are discussed. This discussion provides a rationale for the accumulation of nitrite by the herbicide-treated leaves.

Journal Article↗

PubMed1980

Reduction of Nitrate and Nitrite in Lambsquarters (Chenopodium album) Biotypes Resistant and Susceptible to Atrazine Toxicity.

The nitrite-reducing activity of the normal susceptible biotype of lambsquarters (Chenopodium album L.) was strongly inhibited by atrazine in the assay medium, both in the case of the in vivo assays of leaf discs in light, and in vitro photoreduction assays of crude extracts. In vitro assays of crude extracts with methylviologen or ferredoxin supplying the reducing potential were not inhibited by atrazine. In the resistant biotype, inhibition of nitrite reduction did not occur with any of the above assays. Thus, it appears that atrazine does not inhibit nitrite reductase itself, but rather the availability of photosynthetically supplied electrons for the reduction. Atrazine had no effect when added to the media for either in vivo or in vitro assays of nitrate reduction by either the susceptible or resistant biotype.Young lambsquarters plants were treated with atrazine by spraying the leaves at a rate which was lethal for susceptible plants after 5 or 6 days, but had little effect on the resistant biotype. Nitrite did not accumulate in either biotype, but remained present at the level of about 0.1 microgram nitrite N per gram fresh weight. The nitrate content of susceptible-type leaves did increase to two or three times the initial level, during the first four days after spraying. Usually the only visible effect on the plants during this time was a decreased growth rate. Twenty-four hours after spraying the following activities had fallen to 25% or less of the activities of solvent-sprayed control plants: in vivo nitrite reductase, in vivo nitrate reductase, in vitro NADH-nitrate reductase, in vitro reduced flavin mononucleotidenitrate reductase, and in vitro NADH-diaphorase. In these atrazine-treated plants, in vitro nitrite reductase activity with reducing potential supplied by methylviologen was not affected, nor were any of the above activities in leaves of atrazine-treated resistant plants. The abrupt fall in nitrate reductase represents an effect of atrazine not directly related to inhibition of photosynthesis.

Journal Article↗

PubMed1983

Seed Dormancy in Red Rice : III. Response to Nitrite, Nitrate, and Ammonium Ions.

Sodium nitrite at 10 millimolar breaks dormancy of dehulled red rice (Oryza sativa). While germination is light independent, low pH conditions (pH 3) are required for maximum response. Water and buffer controls at pH 3 remain dormant. The response to nitrite occurs at 25 and 30 degrees C but is reduced at 20 degrees C, although nondormant seeds germinate readily at this temperature. The contact time for response to nitrite is less than 2 h at the start of imbibition. Seeds imbibed first in water show reduced germination when subsequently transferred to nitrite. Dehulled seeds show little or no response to nitrate and ammonium ions.Intact seeds remain dormant in the presence of nitrite or nitrate unless partially dry-afterripened. The pH dependence of nitrite sensitivity is reduced in intact, afterripening seeds. In highly dormant seeds, vacuum infiltration experiments suggest that the hull restricts uptake of nitrite.

Journal Article↗

PubMed1985

The effect of low osmotic potential on nitrite reduction in intact spinach chloroplasts.

The effect of water stress (reduced osmotic potential) on photosynthetic nitrite reduction was investigated using intact, isolated spinach (Spinacia oleracea) chloroplasts. Nitrite-dependent O(2) evolution was inhibited 39% at -29.5 bars osmotic potential, relative to a control at -11 bars. In the presence of an uncoupler of photophosphorylation this inhibition was not seen. Reduced osmotic potential did not inhibit either methyl viologen reduction or photosynthetic O(2) reduction. These results indicate that an inhibition of electron transport to ferredoxin cannot account for the observed inhibition of nitrite-dependent O(2) evolution. In vitro assay of nitrite reductase activity showed that the interaction of the enzyme with nitrite was not affected by changes in the concentrations of ions or molecules that might be caused by water stress conditions. These results indicate that the most likely site for the effect of water stress on chloroplastic nitrite reduction is the interaction of ferredoxin with nitrite reductase.

Journal Article↗

PubMed1979

Toxicity of NO(2): Effect of Nitrite on Microbial Activity in an Acid Soil.

In an acid forest soil of pH 4.0 to 4.2 amended with glucose, 1.0 mug of nitrite-N per g of soil inhibited the rate of O(2) utilization and CO(2) evolution. The inhibition was evident only for several hours after nitrite addition, and the subsequent rate of glucose mineralization was the same as in soil not receiving nitrite. The decomposition of protein hydrolysate was reduced by 10 mug of nitrite-N per g of soil but not lower concentrations, and the inhibition of this process by 20 mug of nitrite-N per g had dissipated after 24 h. Nitrite disappeared readily from this soil. More than 20 mug of bisulfite-S per g of soil was required to inhibit glucose decomposition. The data suggest that the possible antimicrobial effects of low levels of NO(2), which give rise to nitrite in soil, require further evaluation.

Journal Article↗

PubMed1994

Ammonium and Nitrite Inhibition of Methane Oxidation by Methylobacter albus BG8 and Methylosinus trichosporium OB3b at Low Methane Concentrations.

Methane oxidation by pure cultures of the methanotrophs Methylobacter albus BG8 and Methylosinus trichosporium OB3b was inhibited by ammonium choride and sodium nitrite relative to that in cultures assayed in either nitrate-containing or nitrate-free medium. M. albus was generally more sensitive to ammonium and nitrite than M. trichosporium. Both species produced nitrite from ammonium; the concentrations of nitrite produced increased with increasing methane concentrations in the culture headspaces. Inhibition of methane oxidation by nitrite was inversely proportional to headspace methane concentrations, with only minimal effects observed at concentrations of>500 ppm in the presence of 250 muM nitrite. Inhibition increased with increasing ammonium at methane concentrations of 100 ppm. In the presence of 500 muM ammonium, inhibition increased initially with increasing methane concentrations from 1.7 to 100 ppm; the extent of inhibition decreased with methane concentrations of > 100 ppm. The results of this study provide new insights that explain some of the previously observed interactions among ammonium, nitrite, methane, and methane oxidation in soils and aquatic systems.

Journal Article↗

PubMed2001

Metabolic behavior of denitrifying phosphate-accumulating organisms under nitrate and nitrite electron acceptor conditions.

The effects of various types of electron acceptors on anoxic phosphorus uptake were investigated in detail to obtain a better insight into the metabolic behavior of denitrifying phosphate-accumulating organisms. Batch experimental tests under three different electron acceptor conditions, i.e., nitrate, nitrite and mixtures of nitrate and nitrite, were carried out using activated sludge cultivated in a sequencing batch reactor. The experimental results confirmed no inhibition of the utilization of nitrate or nitrite as an electron acceptor for anoxic phosphorus uptake. Anoxic phosphorus uptake occurred provided there was an electron acceptor present regardless of whether it was nitrate or nitrite. However, for nitrite a relatively small amount of anoxic phosphorus was taken up per nitrogen denitrified compared to nitrate. On the other hand, the amount of anoxic phosphorus taken up per nitrogen denitrified increased with an increase in the initial loading amount of electron acceptor in the case of nitrate, whereas it slightly decreased nitrite. Moreover, the amount of phosphorus taken up per nitrogen denitrified decreased with increasing mixed liquor suspended solid (MLSS) concentration in the case of nitrate, while it slightly increased for nitrite. From these results, it was confirmed that the activity of anoxic phosphorus uptake is strongly associated with the type and the initial loading amount of electron acceptor and the MLSS concentration under anoxic conditions.

Journal Article↗

PubMed2000

Nitrite, endothelin and E-selectin plasma levels after arginine infusion in normal, obese and type 2 diabetic subjects.

BACKGROUND: The authors studied the behaviour of nitrites (specific end-products of nitric oxide), endothelin and E-selectin after arginine infusion (biosynthetic precursor of nitric oxide). METHODS: The series consisted of 28 female subjects (mean age 59 +/- 8) of whom: 12 normal controls; 12 suffering from essential obesity (BMI 31.4 +/- 0.7); 14 suffering from uncomplicated type 2 diabetes mellitus. Each subject received intravenous arginine (20 g in two hours); before the infusion and after 1 hour and 2 hours venous blood withdrawal was performed. For each plasma sample the levels of nitrites (colorimetric reaction), endothelin (ELISA method) and E-selectin (ELISA method) were determined. RESULTS: In the controls plasma nitrites decreased significantly (p < 0.05), more evidently at the second hour. In the obese subjects a sharp significant (p < 0.05) fall of nitrites was observed, more evidently at the second hour. In the diabetics nitrite values were reduced (p < 0.05) compared to the baseline. Endothelin levels after arginine were almost unchanged in normal and obese subjects, while in diabetics a significant (p < 0.05) reduction was observed. In the three groups of subjects E-selectin values were not modified by arginine. CONCLUSIONS: This study demonstrates that arginine infusion increase NO biosynthesis in normal, obese and diabetic subjects, inducing a significant reduction of nitrites for an early process of organic reconversion; endothelin showed a reductive trend, mainly in diabetics, probably due to an antagonistic balanced response towards an overproduction of nitric oxide. E-selectin did not change, without correlation with the nitrite and endothelin values, because of an independence from the production of the two "hemodynamic markers".

Analysis of Variance↗