Relative nutritional efficacy of arginine and ornithine salts of alpha-ketoisocaproic acid in traumatized rats

The relative dietary efficacy of arginine alpha-ketoisocaproate (AKIC) and ornithine alpha-ketoisocaproate (OKIC) is evaluated in a rat (Sprague-Dawley) trauma (bilateral femur fracture) model. Both control and traumatized rats were starved for 2 d and then pair-fed for 2 or 4 d one of three liquid diets: diet 1 was a basic casein diet; diets 2 and 3 were the basic diet in which 10% of nitrogen was replaced by AKIC or OKIC nitrogen, respectively. Irrespective of the diet, the protein-efficiency ratio, defined as the gain in body weight per grams nitrogen consumed, was 27% less in traumatized rats than in control rats. More improvement in apparent nitrogen balance, particularly in traumatized rats, was seen with the AKIC supplement. Plasma amino acid patterns demonstrated stimulation of net protein synthesis with AKIC and not with OKIC. Dietary supplementation with AKIC may be beneficial to promote nitrogen economy in trauma victims.

Multiple copies of a DNA sequence from Pseudomonas syringae pathovar phaseolicola abolish thermoregulation of phaseolotoxin production

Phaseolotoxin, a phytotoxin of Pseudomonas syringae pv. phaseolicola, is produced at 18 degrees C but not at 28 degrees C. Here we report that a fragment (24.4 kb) cloned from the wild-type strain, which does not harbour a gene(s) involved in phaseolotoxin biosynthesis, abolishes this thermoregulation in the wild type and suppresses a Tox- mutant at both temperatures. A subclone harbouring a 485 bp fragment contains motifs that are characteristic of DNA-binding sites. In mobility shift assays we have detected a protein(s) from the wild-type and the mutant strains, grown at appropriate temperatures, that specifically binds to the fragment containing the DNA-binding motifs. We propose that the binding protein is a repressor which is 'titrated' by this fragment when it is present in the cell on a multiple copy plasmid, thus allowing expression of phaseolotoxin genes.

Transgenic mice over-producing putrescine in their tissues do not convert the diamine into higher polyamines

We recently described a transgenic mouse line over-expressing the human ornithine decarboxylase gene virtually in all tissues. Despite strikingly elevated tissue putrescine concentrations, no or minimal changes were found in the levels of the higher polyamines spermidine and spermine. We have now extended these studies by further increasing tissue putrescine with the aid of 5-fluoromethylornithine, a specific inhibitor of ornithine transaminase and hence the catabolism of L-ornithine. As a result of the treatment with the latter drug, the concentration of putrescine was further increased by a factor of 2-3 without any changes in the concentrations of spermidine and spermine. In the testis of transgenic mice treated with 5-fluoromethylornithine, the concentration of putrescine was nearly 60 times that in non-transgenic untreated animals, yet the concentration of spermidine was only 1.5-fold higher. A similar small increase in brain spermidine was accompanied by a 40-fold elevation in the concentration of putrescine. The apparent blockade between putrescine and spermidine was in all likelihood not attributable to an inhibition of S-adenosylmethionine decarboxylase, the rate-controlling enzyme in the biosynthesis of spermidine and spermine. Our results are more compatible with the view that in non-dividing adult tissues putrescine is sequestered through some unknown mechanisms in a way that makes it unavailable for the synthesis of the higher polyamines.

Effects of inhibition of ornithine aminotransferase on thioacetamide-induced hepatogenic encephalopathy

Repeated administration of thioacetamide (TAA) to CD1 mice produced hepatic failure and biochemical and behavioral effects characteristic of hepatogenic encephalopathy (HE). The symptoms in mice resembled those previously observed in rats after similar treatments. It is, however, obvious that both in rats and mice the severity of symptoms depends not only on dose and dosing schedule of TAA, but also on strain and body weight (age). Administration of 5-fluoromethylornithine (5FMOrn), a selective inactivator of ornithine aminotransferase (OAT), significantly reduced mortality, and it ameliorated most of the TAA-induced pathologic symptoms, such as hypothermia, decreased locomotor and exploratory behavior, pathologic liver function and amino acid patterns. The most prominent biochemical consequence of 5FMOrn administration is the elevation of ornithine concentrations in tissues, including the brain, and in body fluids. Elevated ornithine concentrations are, therefore, the most likely basis for the therapeutic effects of 5FMOrn. In agreement with this notion is the enhancement of citrulline and urea formation. These findings and the observation that administration of ornithine in combination with a branched-chain 2-oxoacid ameliorated the pathologic symptoms of portal-systemic encephalopathy suggest inhibition of OAT in the treatment of this disease. The liver protective effect of 5FMOrn is not yet understood; the enhancement of regenerative processes is a likely explanation.

Stimulation and inhibition of polymorphonuclear leukocytes phagocytosis by lipoamino acids isolated from Serratia marcescens

The role of the lipoamino acids (serratamolide and ornithine lipid), membrane lipid components of Serratia marcescens, was examined in phagocytosis and phagosome-lysosome fusion of human peripheral polymorphonuclear leukocytes. A mutant strain of Serratia marcescens (NS 38-09) lacking serratamolide was actively phagocytosed by human PMN, while the wild-type strain (NS 38) producing serratamolide was more resistant to phagocytosis by human PMN. Phagocytosis of killed Staphylococcus aureus coated with lipoamino acid (serratamolide), showed that they were more resistant to phagocytosis by PMN, while the cells coated with ornithine lipid or serratamic acid were phagocytosed more actively. Staphylococci coated with phosphatidylethanolamine or phosphatidylglycerol had no significant effect on phagocytosis by PMN. Phagosome-lysosome fusion by PMN labelled with acridine orange was examined by fluorescence microscopy. The fusion indices of lipoamino acid-coated staphylococci were the same as that of controls. Further, ornithine lipid-coated staphylococci stimulated the release of superoxide anion from PMN slightly, but serratamolide did not. These results suggested that serratamolide may contribute to the virulence of S. marcescens in vitro.

Induction of macrophage parasiticidal activity by Staphylococcus aureus and exotoxins through the nitric oxide synthesis pathway

Murine peritoneal macrophages stimulated in vitro with killed Gram-positive bacteria Staphylococcus aureus or its membrane components in the presence of interferon-gamma (IFN-gamma) expressed high levels of nitric oxide (NO) synthase and produced large amounts of NO in a dose-dependent manner. This is not due to the contamination by Gram-negative endotoxin because the stimulatory activity was not affected by the addition of polymyxin B. The expression of the NO synthase and the synthesis of NO by macrophages stimulated with toxic shock syndrome toxin-1 (TSST), lipoteichoic acid (LTA) or killed whole S. aureus together with IFN-gamma was inhibited by the glucocorticoid, dexamethasone or by the specific inhibitor of NO synthesis, L-N-iminoethyl-ornithine (L-NIO). The exotoxins together with IFN-gamma also activated macrophages to kill the intracellular parasite Leishmania major. The leishmanicidal activity was completely inhibited by L-NIO.

Enhanced endogenous ornithine concentrations protect against tonic seizures and coma in acute ammonia intoxication

Pretreatment of mice with 5-fluoromethylornithine (5FMOrn), a selective inactivator of ornithine aminotransferase, diminishes the accumulation of ammonia in the brain after administration of ammonium acetate, and antagonizes ammonia-induced fatal tonic extensor convulsions. In about 50% of the treated animals the loss of the righting reflex and coma is prevented. Presumably these effects are based on the enhancement of urea formation by the increased liver ornithine concentrations. However, since brain ornithine concentrations are greatly enhanced by 5FMOrn, it is not excluded that ornithine has direct effects on cellular events involved in ammonia-induced seizure generation, even though 5FMOrn had no anticonvulsant properties in a series of established animal seizure models, including N-methyl-D,L-aspartate-induced convulsions. NMDA receptor antagonists are capable of preventing death, but do not protect against the generation of coma and tonic extensor convulsions in ammonium acetate intoxicated mice. Since no evidence was found for ammonia-induced glutamate release from rat hippocampus, there is no convincing evidence for the idea that the tonic convulsions are mediated by NMDA receptors. L-Methionine-D, L-sulfoximine (MSO)-induced seizures can be partially antagonized by pretreatment with 5FMOrn. However, the effect is considerably smaller than against ammonia-induced convulsions, although at the time of seizure onset brain ammonia levels of MSO-intoxicated mice were lower than in the animals receiving ammonium acetate. This suggests that MSO-convulsions are not entirely due to the elevation of brain ammonia concentrations, even though MSO administration mimics effects of ammonia on cortical inhibitory neuronal interactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Protective effects of inhibitors of nitric oxide synthase in immune complex-induced vasculitis

1. The ability of analogues of L-arginine (N-iminoethyl-L-ornithine (L-NIO), NG-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine methyl ester (L-NAME) and NG-nitro-L-arginine (L-NNA)) to protect against inflammatory injury induced by activated neutrophils was investigated in rats following intradermal or intrapulmonary deposition of immune complexes. 2. The descending order of potency for protective effects of these analogues was: L-NIO > L-NMMA > L-NNA = L-NAME. The approximate IC50 value for L-NIO in the dermal vasculitis model was 65 microM. For all other compounds, the IC50 values were > 5 mM. 3. The protective effect of L-NIO in the skin was reversed in a dose-dependent manner by the presence of L-arginine, but not by D-arginine. L-Arginine also reversed the protective effects of L-NIO in immune complex-induced lung injury. 4. The protective effects of L-NIO were not associated with reductions in neutrophil accumulation, as measured by extraction from tissues of myeloperoxidase. 5. These data demonstrate that L-NIO has the most potent protective effects against immune complex-induced vascular injury induced by activated macrophages. Furthermore, they indicate that this injury is dependent upon the generation of nitric oxide.

Altered tissue polyamine levels due to ornithine-alpha-ketoglutarate in traumatized growing rats

All cells contain significant amounts of polyamines (PA), and their concentrations are highly regulated. Metabolic activity within a tissue may be reflected in the amount of intracellular PA. Since trauma involves accelerated death and regeneration of tissues, the related levels of PA in extracellular and intracellular fluids may reflect altered protein metabolism. Trauma induces an increased excretion of urinary PA, and the tissues responsible for this whole-body activity are not known. During posttraumatic nutritional management, supplementation with ornithine-alpha-ketoglutarate (OKG) seems to improve nitrogen economy. The present study evaluates the significance of muscle, liver, and intestine PA responses in traumatized (bilateral femur fractures) rats to the feeding of an isonitrogenous liquid diet supplemented with or without OKG. Uninjured control rats were pair-fed with respective traumatized rats. After 2 days of starvation and 4 days of feeding, the traumatized and control rats were killed and the tissues were excised and analyzed. Starvation decreases and refeeding increases urinary PA excretion. Trauma-induced PA response is predominantly seen in muscle tissues, and this may be responsible for parallel increases in PA excretion. Liver PA responses show a varying tendency confirming the increased protein synthetic activity due to trauma. Intestine has the highest intracellular PA levels, and there is a general smaller (statistically insignificant) increase in all the individual PA contents due to trauma. OKG supplementation augments tissue and urine PA responses in control rats; however, in trauma rats muscle PA levels show very little change, although nitrogen retention is significantly better (88% to 77%). Mechanistic studies are needed to evaluate the significances of the time-dependent, injury-induced, individual intracellular PA levels.

Ornithine alpha-ketoglutarate and glutamine supplementation during refeeding of food-deprived rats

The aim of this study was to compare the efficiency of ornithine alpha-ketoglutarate (OKG) and glutamine supplementation in an experimental model of denutrition that provides well-characterized disturbances of amino acid patterns. Male Wistar rats (187 +/- 11 g; five in each group) were starved for 3 days and then refed for 7 days with an oral diet (192 kcal kg-1.day-1 and 2.25 g of nitrogen kg-1.day-1), supplemented with 0.19 g of nitrogen kg-1.day-1 in the form of OKG, glutamine, or casein (control group). Food deprivation induced a fall in most tissue amino acids, with the notable exception of muscle leucine and liver glutamate, which increased by 43% (p < .01), and 11% (p < .05), respectively. The main effect of OKG was seen in the viscera, with a normalization of most amino acid pools (including proline and branched-chain amino acids) in the small bowel and liver. The main effect of glutamine was observed in the muscle, with a normalization of the glutamine and leucine pools. We conclude that, in this model and with the doses used, OKG and glutamine act in different target tissues, ie, splanchnic areas and muscle, respectively.

Inhibition of hog liver folylpolyglutamate synthetase by 5-substituted 5,8-dideaza analogues of folic acid bearing a terminal L-ornithine residue

Five new N alpha-(5,8-dideazapteroyl)-L-ornithines have been prepared using multistep synthetic sequences. These include N alpha-[5-(trifluoromethyl)-5,8-dideazapteroyl]-L-ornithine, 3, as well as N alpha-[5-(trifluoromethyl)-5,8-dideazaisopteroyl]-L-ornithine, 4, and its 5-fluoro and 5-chloro analogues. Both of the compounds containing a 5-(trifluoromethyl) group (3 and 4) were found to be excellent inhibitors of homogeneous hog liver folylpolyglutamate synthetase, having Ki values in the same range as N alpha-(5-chloro-5,8-dideazapteroyl)-L-ornithine, 2, (approximately 10 nM). However, the bridge-reversed isomer of 2 was 60-fold less inhibitory than 2.

The molecular mechanism of central analgesia induced by morphine or carbachol and the L-arginine-nitric oxide-cGMP pathway

The role of the L-arginine-NO-cGMP pathway in morphine-induced central analgesia was investigated in two nociceptive tests: PGE2-induced hind paw hyperalgesia and tail-flick. The central analgesic effect of morphine was potentiated by MY5445, a specific cGMP phosphodiesterase inhibitor. I.c.v. injections of morphine or carbachol caused dose-dependent analgesia, which was prevented by methylene blue, an inhibitor of guanylate cyclase. The NO synthase inhibitor, N-iminoethyl-L-ornithine, prevented carbachol-induced analgesia, but did not affect morphine-induced analgesia. Our results suggest that activation of cGMP may underlies analgesia induced by morphine and carbachol. The activation of guanylate cyclase by carbachol seems to depend on the L-arginine-NO pathway, but that caused by morphine remains to be further characterized.

A perfusion system for the long term study of macrophage activation

1. A closed system was developed for perfusing J774 macrophages in columns. The cells were perfused for up to 100 h, at which time they were still viable. 2. Stimulation with increasing concentrations (0.01-10 micrograms ml-1) of bacterial lipopolysaccharide (LPS) caused the cells to produce increasing amounts of nitrite in the perfusion medium. This production was time-dependent, reaching a plateau by 48-50 h. 3. The nitrite accumulation caused by 0.1 microgram ml-1 of LPS was augmented by priming the cells for 2 h with increasing amounts of interferon-gamma. The nitrite accumulation also reached a plateau under these conditions. 4. N-iminoethyl-L-ornithine (L-NIO, 30 microM) completely inhibited the accumulation of nitrite whereas dexamethasone (0.3 microM) caused 60-70% inhibition. 5. Perfusion of the cells without L-arginine prevented the nitrite accumulation. Replacement of this amino acid after 20 or 50 h of perfusion led to a rapid generation of nitrite, the levels of which continued to increase for the duration of the experiment. 6. Thus, the perfusion system can be used to study the kinetics of the activation of the NO synthase and most likely other parameters in J774 cells and probably other cells in culture. An observation already of interest is that the 'disappearance' of the NO synthase after its activation can be prevented or reduced by removal of L-arginine from the medium.

Origin, structure, and regulation of argK, encoding the phaseolotoxin-resistant ornithine carbamoyltransferase in Pseudomonas syringae pv. phaseolicola, and functional expression of argK in transgenic tobacco

Pseudomonas syringae pv. phaseolicola produces the tripeptide N delta(N'-sulfo-diaminophosphinyl)-ornithylalanyl-homoarginin e (phaseolotoxin), which functions as a chlorosis-inducing toxin in the bean halo blight disease by inhibiting ornithine carbamoyltransferase (OCT). The bacterium possesses duplicate OCT genes, one of which, argK, encodes a toxin-resistant enzyme (ROCT) and imparts resistance to phaseolotoxin. We sequenced the argK gene from strain NPS3121, defined its promoter region, analyzed its regulation, and characterized its transcripts. The gene probably originated from another organism, since it is very distantly related to the argF gene encoding the housekeeping toxin-sensitive OCT and has low G+C content compared with the bacterial genome as a whole and with other protein-coding genes from P. syringae pv. phaseolicola. Optimized alignments of 13 OCT sequences allowed us to define key residues that may be responsible for toxin resistance and to identify a distinct prokaryotic amino acid signature, in ROCT, which argues for a prokaryotic origin of argK. An in-frame fusion of the argK coding region with the chloroplast transit peptide segment of the pea rbcS gene was introduced in Nicotiana tabacum by Agrobacterium-mediated transformation. The presence of an ROCT activity in transgenic plants was demonstrated by in vitro and in vivo assays. Some plants were toxin resistant, suggesting that pathogen-derived resistance to the toxin should be feasible in the pathogen's host.

Expression of a bacterial phaseolotoxin-resistant ornithyl transcarbamylase in transgenic tobacco confers resistance to Pseudomonas syringae pv. phaseolicola

Toxins have been shown to be an important virulence component for most pathovars of Pseudomonas syringae. Here we have examined the role of phaseolotoxin in the virulence mechanism of P. syringae pv. phaseolicola by producing transgenic tobacco plants that express a pathogen-derived toxin-resistant target enzyme. Such plants are insensitive to the toxin and less prone to infection by the pathogen.

Nitric oxide mediates tumor necrosis factor-alpha cytotoxicity in endothelial cells

Tumor necrosis factor alpha (TNF-alpha) exerts multiple actions on endothelial cells including among others the expression of pro-coagulant activity and adhesion molecules, and secretion of cytokines. We now show that TNF-alpha induces a time- and dose-dependent cytotoxic effect on cultured bovine aortic endothelial cells. This TNF-induced cytotoxicity, which is preceded by increased production of nitric oxide (NO), is significantly decreased by the NO synthase inhibitor N-iminoethyl-L-ornithine (L-NIO). Dexamethasone, which prevents the expression of cytokine-induced NO synthase in endothelial cells, also inhibits TNF-alpha-dependent cytotoxicity. The results indicate that NO is involved in the cytotoxic effect of TNF-alpha on endothelial cells.

Global degranulation of rat mast cells stimulated with DNP-polystyrene

Mediator release was studied in rat peritoneal mast cells sensitized with a mouse monoclonal anti-DNP IgE antibody, and stimulated with DNP-ornithine covalently attached to radio-derivatized polystyrene petri dishes. Cells releasing serotonin at maximal rates were investigated by transmission electron microscopy. Generalized exocytosis of granules could be observed, suggesting non-directional release of mediators, and non-compartmentalized action of second messengers in mast cells stimulated with polystyrene-bound DNP. Stimulation of sensitized mast cells by DNP covalently bound to the rigid polystyrene surface is consistent with extrinsic mechanisms proposed for Fc(epsilon)RI receptor action, and suggests that internalization of Fc(epsilon)RI is not needed for triggering cell degranulation.

Nitric oxide functions as an inhibitor of platelet adhesion under flow conditions

BACKGROUND

Nitric oxide (NO) has been identified as endothelium-derived relaxing factor (EDRF), which, in addition to its relaxant effects on vascular smooth muscle cells, is also a potent inhibitor of platelet aggregation. An inhibitory role on platelet adhesion has been suggested from experiments with washed platelets under static conditions. We have determined whether endothelium-derived and exogenous NO also regulates platelet adhesion in whole blood under flow conditions.

METHODS AND RESULTS

The effect of endothelium-derived NO was studied by the addition of specific inhibitors of NO production, L-N-monomethyl arginine (L-NMMA) and N-iminoethyl-L-ornithine (L-NIO), to a perfusion system in which both endothelial cells and their matrices were present. A concentration-dependent increase in platelet adhesion to the matrix was found with a maximum inhibition at a concentration of 2 mM L-NMMA and 0.1 mM L-NIO. The effect was dependent on the presence of endothelial cells, because no increase in platelet adhesion was observed in their absence. The effect of exogenous NO was tested in a specially devised perfusion system in which the NO was introduced at the site of adhesion by means of a porous membrane on which an extracellular matrix of endothelial cells was present. Inhibition of platelet adhesion by NO was found at all shear rates tested and after all perfusion periods.

CONCLUSIONS

These results demonstrate that NO is a potent inhibitor of platelet adhesion under flow conditions and thereby contributes to the regulatory role of vascular endothelial cells on platelet-vessel wall interaction.

Inhibition of ornithine aminotransferase by 5-fluoromethylornithine: protection against acute thioacetamide intoxication by elevated tissue ornithine levels

5-Fluoromethylornithine (5FMOrn) is a selective inactivator of ornithine aminotransferase. Its administration causes a dramatic increase of ornithine concentrations in all tissues. Treatment of mice with 20 mg.kg-1 5FMOrn shortly before or after a lethal dose (600 mg.kg-1, intraperitoneally) of thioacetamide (TAA), followed by a second dose 24 hr later, prevented death of 60% of the mice. Pathologic symptoms of TAA intoxication (liver haemorrhage, elevation of amino acids in blood and tissues, diminution of liver spermidine and spermine concentrations, elevation of the activity of liver enzymes in the plasma) were significantly ameliorated by the treatment. The liver protective action of 5FMOrn is related to the elevation of ornithine concentration, as appears from the fact that other, less selective inactivators of ornithine aminotransferase, also produced some protection against acute intoxication with TAA, but not a structurally related compound with no effect on this enzyme.

Role of nitric oxide synthesis in the regulation of coronary vascular tone in the isolated perfused rabbit heart

OBJECTIVE

The aim was to study the effects on coronary vascular tone of three inhibitors of nitric oxide (NO) synthesis.

METHODS

Studies were performed on isolated perfused hearts of 74 male New Zealand White rabbits fed normal laboratory diet. Resting coronary perfusion pressure was increased to 40-60 mm Hg with the thromboxane mimetic 9,11-dideoxy-9 alpha,11 alpha-methanoepoxy prostaglandin F2 alpha (U46619). The effects of NG-monomethyl-L-arginine (L-NMMA), N-iminoethyl-L-ornithine (L-NIO), and NG-nitro-L-arginine methyl ester (L-NAME) (0.3-300 microM) on resting coronary perfusion pressure were determined. The effects of these compounds, at concentrations that increased the resting perfusion pressure to a similar extent, on the fall in perfusion pressure induced by acetylcholine (0.1 microM) and glyceryl trinitrate (1 microM) were also investigated. In these studies the resting perfusion pressure was maintained at 40-60 mm Hg by reducing the concentration of U46619.

RESULTS

L-NMMA, L-NIO, and L-NAME induced concentration dependent increases in resting coronary perfusion pressure (n = 3-9, p < 0.05). L-NAME had the greatest potency and efficacy, increasing the resting pressure by 48.0(SEM 9.6) mm Hg at 30 microM. L-NIO and L-NMMA increased perfusion pressure by 27.3(3.0) and 19.5(5.8) mm Hg respectively at the maximum concentration studied (300 microM). However, at concentrations that were equieffective on resting perfusion pressure (15 mm Hg increase), L-NMMA (100 microM), but not L-NIO (25 microM) or L-NAME (4 microM), significantly inhibited the fall in pressure induced by acetylcholine by 57.2(5.0)%, n = 6, p < 0.05. This effect of L-NMMA++ was attributed to a shorter duration of fall and was reversed by L-arginine (300 microM). L-NMMA (100 microM) and L-NIO (25 microM) potentiated the effect of glyceryl trinitrate by increasing the peak fall in perfusion pressure by 75.6(11.0)% and 68.8(24.1)% respectively (n = 6 for each, p < 0.05).

CONCLUSIONS

The differential effects of the three inhibitors on resting coronary perfusion pressure and the acetylcholine induced fall in coronary perfusion pressure suggest that basal and stimulated NO synthesis may be differentially regulated. Reduction in the synthesis of endogenous NO by these compounds potentiates the glyceryl trinitrate induced fall in perfusion pressure, which may have important clinical implications.

Identification of inhibitors of nitric oxide synthase that do not interact with the endothelial cell L-arginine transporter

The effects of inhibitors of nitric oxide (NO) synthase and other cationic amino acids on unidirectional L-arginine transport were studied in porcine aortic endothelial cells cultured in microwell plates or perfused in microcarrier columns. L-Homoarginine, L-lysine and L-ornithine inhibited transport of L-arginine. The NO synthase inhibitors NG-monomethyl-L-arginine and NG-iminoethyl-L-ornithine also reduced L-arginine uptake, whereas NG-nitro-L-arginine and its methyl-ester had no inhibitory effect. The ability to modulate selectively endothelial cell L-arginine transport or NO synthase activity will allow further characterization of the arginine transporter and its role in regulating NO biosynthesis.

Regulation of IL-2 production by mononuclear cells from rheumatoid arthritis synovial fluids

Products of polyamine oxidation down-regulate IL-2 production by peripheral blood T cells. We show here that the production of IL-2 by rheumatoid arthritis synovial fluid mononuclear cells is inversely correlated with the concentrations of polyamines in these cells. In addition, the inhibition of polyamine biosynthesis or oxidation in cultures of these cells enhances their ability to produce IL-2. Our findings suggest that polyamine oxidation plays an important role in the suppression of T cell function characteristic of rheumatoid arthritis synovial fluids.

Synthesis and inhibiting properties toward trypsin like proteases of N alpha-(N,N-dimethylcarbamoyl)-alpha-azaornitine and alpha-azalysine esters

N alpha-(N,N-dimethylcarbamoyl)-alpha-azaornitine and N alpha-(N,N-dimethylcarbamoyl)-alpha-azalysine phenyl and p-nitrophenyl esters (7-10) were synthesized and tested as inhibitors of trypsin, chymotrypsin and thrombin. The N,N-dimethylcarbamoyl group was chosen to decrease the tendency of acylcarbazates to cyclization into 1,3,4-oxadiazol-2(3H)-ones. Only the p-nitrophenyl alpha-azaornithine derivative 8 was inactivated rapidly by intramolecular acylation of the terminal amino group, rather than by cyclization to oxadiazolone, in aqueous solution at pH 8. The corresponding alpha-azalysine derivative 10 is completely unaffected under the same conditions. Rapid inactivation of thrombin and trypsin only was observed for all alpha-azapeptide esters 7-10 at 0.5 mM inhibitor concentration. No proteolytic activity was restored after 24 h following 2,000 fold dilution of the inhibitor concentration suggesting formation of very stable acylenzymes.