Human brain contains a metalloprotease that converts big endothelin-1 to endothelin-1 and is inhibited by phosphoramidon and EDTA

Incubation of big endothelin-1 (bET-1) with protein derived from the detergent-extracted 100,000 g pellet prepared from human brain tissue resulted in the formation of endothelin-1 (ET-1) at a rate of 90 fmol mg-1 protein min-1. This formation was inhibited in a concentration-dependent manner by either phosphoramidon or EDTA, with half-maximal inhibitory concentrations of 2 and 20 microM, respectively. No conversion of big endothelin-3 (bET-3) to endothelin-3 (ET-3) was detected under the same conditions. These results show the presence in the human brain of a metalloprotease-like enzymatic activity which selectively converts bET-1 and ET-1. Together with earlier reports of mRNA for ET-1 this suggests the presence of the entire synthetic pathway for ET-1 in human brain.

Ca2+/calmodulin-regulated nitric oxide synthases

NO synthase (NOS) catalyzes the oxidation of L-arginine to L-citrulline and nitric oxide (NO) or a NO-releasing compound. At least three isoforms of NOS exist (types I-III). The activities of the type I isoform purified from brain and the type III isoform purified from endothelial cells are regulated by the intracellular free calcium concentration ([Ca2+]i) and the Ca(2+)-binding protein calmodulin. At resting [Ca2+]i, both isozymes are inactive; they become fully active at [Ca2+]i greater than or equal to 500 nM Ca2+. Longer lasting increases in [Ca2+]i may downregulate NO formation, for in vitro phosphorylation by Ca2+/calmodulin protein kinase II decreases the Vmax of NOS. Besides the conversion of L-arginine, type I NOS, Ca2+/calmodulin dependently, generates H2O2 and reduces cytochrome c/P450. Other redox activities, i.e. the reduction of nitroblue tetrazolium to diformazan (NADPH-diaphorase) or of quinoid-dihydrobiopterin to tetrahydrobiopterin, by NOS appear to be Ca2+/calmodulin-independent.

Induction of NADPH-dependent diaphorase and nitric oxide synthase activity in aortic smooth muscle and cultured macrophages

Lipopolysaccharide (LPS), either alone or in combination with cytokines, induces nitric oxide (NO) synthase activity in cells that normally release little or no NO. In arterial smooth muscle cells and various macrophage cell lines, NO synthase activity is induced after several hours of incubation with LPS. In brain, NADPH-dependent diaphorase activity has been associated with constitutive NO synthase. Here we show that incubation of rat aorta or cultured macrophages with LPS causes a time-dependent induction of NO synthase. The NO synthase activity in both rat aorta and macrophages was calcium independent and inhibited by NG-monomethyl-L-arginine and NG-nitro-L-arginine. We also found that LPS caused a time-dependent induction in NADPH-dependent diaphorase activity in both rat aorta and cultured macrophages. The diaphorase activity was mainly NADPH dependent and NADH independent. NO synthase activity and NADPH-diaphorase activity in crude cytosol from LPS-treated macrophages were found to co-purify, using 2',5'-ADP-Sepharose followed by Superose-6 gel permeation chromatography.

Interactions of endothelins and EDRF in bovine native endothelial cells: selective effects of endothelin-3

The tone of vascular smooth muscle is influenced by factors released from the endothelium, including endothelin (ET)-1 and endothelium-derived relaxing factor (EDRF). To better understand the interactions between these two mediators, we examined the release of both immunoreactive ET-1 (ir-ET-1) and EDRF from bovine aortic intact endothelium. Bovine aortas were opened longitudinally, washed, and clamped with the endothelium uppermost between two plates. The upper plate contained six openings forming identical and independent wells of endothelial cell monolayer. In experiments examining the release of EDRF, measured as accumulated NO2- and NO3- (NO chi -), we found that ET-3, calcium ionophore A23187 (A23187), acetylcholine (ACh), or ADP caused significant increase in NO chi- release, whereas ET-1 did not. These were significantly reduced in the presence of the EDRF/NO synthase inhibitor, NG-methyl-L-arginine (L-NMA). In a parallel series of experiments measuring EDRF release by stimulation of guanosine 3',5'-cyclic monophosphate (cGMP) accumulation in rat fetal lung (RFL)-6 cells, ET-3 but not ET-1 was also found to be active as a releaser of EDRF. A23187 caused an increase of ir-ET-1 release, whereas ACh, ADP, or the NO-containing compound sodium nitroprusside decreased the release of ir-ET-1. The depression in ir-ET-1 release in the presence of ACh or ADP was not seen when the endothelium was treated with L-NMA. When the cells were pretreated with 8-bromoguanosine 3',5'-cyclic monophosphate (8-bromo-cGMP), the release of ir-ET-1 in response to A23187 was significantly depressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Colocalization of nitric oxide synthase and NADPH-diaphorase in cultured myenteric neurones

Nitric oxide synthase immunoreactivity and NADPH-diaphorase activity were examined in explant culture preparations of the myenteric plexus from beneath the taenia coli of the guinea-pig caecum. Nitric oxide synthase immunoreactive neurones formed approximately one third of the total neuronal population. NADPH-diaphorase positive neurones, demonstrated histochemically, constituted a similar proportion of the total number of neurones. Immunocytochemistry and NADPH-diaphorase histochemistry performed on the same preparations revealed that all nitric oxide synthase immunoreactive neurones expressed NADPH-diaphorase activity. This histochemical evidence is consistent with the view that nitric oxide may act as a regulatory agent in the guinea-pig caecum.

Regulation and subcellular location of nitrogen oxide synthases in RAW264.7 macrophages

In nitrinergic signal transduction, nitrogen oxide (NO) synthases (NOS) (EC 1.14.23) catalyze the conversion of L-arginine to L-citrulline and NO, which in turn activates soluble guanylyl cyclase. Macrophages were reported to contain a single isoform of NOS (type II, soluble, Ca(2+)-independent, 130-kDa) and only upon activation of the cells by interferon-gamma (INF) and lipopolysaccharides (LPS). By a mechanism involving L-type Ca2+ channels, calmodulin, and serine proteases, INF/LPS also induce a cytotoxic activation of macrophages. In RAW264.7 macrophages, NO release was detected upon activation of the cells by INF/LPS but also, although at a 20-fold lower level, in control cells. The latter constitutive NOS activity and NO release were Ca2+ dependent and were decreased in INF/LPS-activated RAW264.7 cells or with increasing passage number. RAW264.7 cells did not express soluble guanylyl cyclase, suggesting other target molecules for NO. In INF/LPS-activated cells, NOS activities and NO release were Ca2+ independent (type II) and coinduced with NADPH-diaphorase activities both in the soluble and in the particulate fractions. The NOS-II activities corresponded to a 130-kDa protein, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which was not recognized in a protein immunoblot with anti-NOS-I antibody. The serine protease inhibitor tosyl-lysyl chloromethyl ketone abolished the induction of NOS-II by INF/LPS, by depleting intracellular thiol pools and interfering with protein synthesis. Induction of NOS-II by INF/LPS was transcriptionally based and, for maximal enzyme activity, required increased intracellular tetrahydrobiopterin levels, intracellular Ca2+ mobilization, and activation of non-L-type Ca2+ channels but, unlike the induction of macrophage-mediated cytotoxicity, neither L-type-Ca2+ channels nor calmodulin.

Ca2+/calmodulin-dependent NO synthase type I: a biopteroflavoprotein with Ca2+/calmodulin-independent diaphorase and reductase activities

NO synthase (NOS; EC 1.14.23) catalyzes the conversion of L-arginine into L-citrulline and a guanylyl cyclase-activating factor (GAF) that is chemically identical with nitric oxide or a nitric oxide-releasing compound (NO). Similar to the other isozymes of NOS that have been characterized to date, the soluble and Ca2+/calmodulin-regulated type I from rat cerebellum (homodimer of 160-kDa subunits) is dependent on NADPH for catalytic activity. The enzyme also possesses NADPH diaphorase activity in the presence of the electron acceptor nitroblue tetrazolium (NBT). We investigated the requirements of NOS and its content of the proposed additional cofactors tetrahydrobiopterin (H4biopterin) and flavins, further characterized the NADPH diaphorase activity, and quantified the NADPH binding site(s). Purified NOS type I Ca2+/calmodulin-independently bound the [32P]2',3'-dialdehyde analogue of NADPH (dNADPH), which, at near Km concentrations during 3-min incubations was utilized as a substrate and at higher concentrations or after prolonged incubations and cross-linking inhibited NOS activity. The NADPH diaphorase activity was Ca2+/calmodulin-independent, required higher NADPH concentrations than NOS activity, and was affected by dNADPH to a lesser degree. Divalent cations interfered with the diaphorase assay. Per dimer, native NOS contained about 1 mol each of H4biopterin, FAD, and FMN, classifying it as a biopteroflavoprotein, and incorporated 1 mol of dNADPH. No dihydrobiopterin (H2biopterin), biopterin, or riboflavin was detected. These findings suggest that NOS may share cofactors between two identical subunits via high-affinity binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin secretion from pancreatic B cells caused by L-arginine-derived nitrogen oxides

L-arginine causes insulin release from pancreatic B cells. Data from three model systems support the hypothesis that L-arginine-derived nitrogen oxides (NOs) mediate insulin release stimulated by L-arginine in the presence of D-glucose and by the hypoglycemic drug tolbutamide. The formation of NO in pancreatic B cells was detected both chemically and by the NO-induced accumulation of guanosine 3',5'-monophosphate. NG-substituted L-arginine analogs inhibited the release of both insulin and NO. Protein immunoblot and histochemical analysis with antiserum to type I NO synthase suggest that the formation of NO in pancreatic B cells is catalyzed by an NADPH- (reduced form of nicotinamide adenine dinucleotide phosphate), Ca2+/calmodulin-dependent type I NO synthase of about 150 kilodaltons.

Induced RAW 264.7 macrophages express soluble and particulate nitric oxide synthase: inhibition by transforming growth factor-ß

RAW 264.7 macrophages induced with lipopolysaccharide and interferon-gamma expressed nitric oxide (NO) synthase. Approximately two-thirds of the total induced NO synthase activity was found in the cytosolic fraction, whereas one-third was associated with the particulate fraction. Both enzymes formed L-citrulline in addition to NO-like material. NO and L-citrulline formation by both enzymes were calcium-independent and inhibited by NG-nitro-L-arginine and NG-methyl-L-arginine. Transforming growth factor-beta 1 prevented the induction of both enzymes.

Purification and characterization of a human NO synthase

A NO synthase (NOS, EC 1.14.23) was isolated from human cerebellum by two sequential chromatography steps, that is affinity chromatography on 2'5'ADP sepharose and size exclusion chromatography on Superose 6. Human NOS migrated as a single band of 160 kDa on SDS/PAGE. The enzyme was Ca2+/calmodulin-regulated and NADPH/tetrahydrobiopterin (BH4)-dependent, which are characteristics of a type I NOS previously isolated from rat cerebellum. Antisera raised against purified rat cerebellar NOS crossreacted specifically with a 160 kDa protein in crude supernatant fraction of human cerebellum and purified human NOS but not in crude supernatant fraction of the temporal lobe. These findings provide evidence that nitrinergic signal transduction through conversion of L-arginine to L-citrulline and NO does also occur in humans and NO may function as a neurotransmitter in the human central nervous system.

Purification and characterization of particulate endothelium-derived relaxing factor synthase from cultured and native bovine aortic endothelial cells

The particulate enzyme responsible for the synthesis of endothelium-derived relaxing factor has been purified from cultured and native (noncultured) bovine aortic endothelial cells. Purification of the solubilized particulate enzyme preparation by affinity chromatography on adenosine 2',5'-bisphosphate coupled to Sepharose followed by Superose 6 gel filtration chromatography resulted in a single protein band after denaturing polyacrylamide gel electrophoresis that corresponded to approximately 135 kDa. The enzyme activity in the various fractions was assayed by its stimulatory effect on soluble guanylyl cyclase of rat fetal lung fibroblasts (RFL-6 cells), by the formation of L-citrulline from L-arginine, by measuring nitrite/nitrate formation, and by bioassay on endothelium-denuded vascular strips. Endothelium-derived relaxing factor synthase was purified 3419-fold from the crude particulate fraction of cultured bovine aortic endothelial cells with a 12% recovery (RFL-6 assay). Purified endothelium-derived relaxing factor synthase required L-arginine, NADPH, Ca2+, calmodulin, and 5,6,7,8-tetrahydrobiopterin for full activity.

Endothelial cells have a particulate enzyme system responsible for EDRF formation: measurement by vascular relaxation

Endothelium-derived relaxing factor (EDRF) released from endothelial cells (EC) has been shown to be nitric oxide (NO) or a closely related molecule. In cultured EC, the enzyme responsible for the formation of EDRF, EDRF-synthase, was initially described as being cytosolic, but more recently we have found it to be predominantly particulate. In view of this discrepancy we have investigated the EDRF synthesizing activity of cytosolic and particulate fractions isolated from native bovine aortic EC. EDRF was measured by cGMP formation in rat fetal lung cultured fibroblasts (RFL-6) and by the ability of cell fractions to relax endothelium-denuded, preconstricted rabbit aortic strips. Cytosolic fractions from native EC (100 micrograms) had no effect on the tone of rabbit aortic strips and little effect on cGMP levels in RFL-6 cells in the presence of L-arginine and NADPH (100 microM). However, under the same conditions the 100,000 x g pellet fractions relaxed rabbit aortic strips and increased cGMP levels in RFL-6 cells. Thus EDRF synthase from native EC, like those grown in culture, is located mainly in the particulate fraction.

Calmodulin-dependent endothelium-derived relaxing factor/nitric oxide synthase activity is present in the particulate and cytosolic fractions of bovine aortic endothelial cells

Endothelium-derived relaxing factor/nitric oxide (EDRF/NO) synthesized by bovine aortic endothelial cells and subcellular fractions thereof was assayed by its stimulating effect on soluble guanylyl cyclase of rat fetal lung fibroblasts (RFL-6 cells). The release of EDRF/NO by intact endothelial cells could be stimulated with bradykinin, thrombin, or ADP and was abolished in Ca2(+)-free medium. When subcellular fractions were analyzed, some EDRF/NO-synthesizing activity was found in the cytosolic fraction, but most of the activity was associated with the particulate fraction. Both enzyme activities required L-arginine and NADPH for EDRF/NO synthesis, both were inhibited by NG-nitro-L-arginine and NG-methyl-L-arginine, and hemoglobin or methylene blue abolished the effect of the EDRF/NO produced by both enzymes. Both enzymes were highly sensitive to Ca2+; the major increase in activity occurred between 100 and 500 nM free Ca2+. Exposure of the particulate enzyme activity to 1 M KCl removed 39% of the protein and reduced total activity by 46%, but the activity was restored when exogenous calmodulin (CaM) was added. Further KCl washes caused little further loss of protein or EDRF/NO synthase activity. The KCl-washed particulate enzyme could be solubilized with the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate. The CaM antagonists calmidazolium and trifluoperazine as well as the CaM-binding protein calcineurin inhibited the EDRF/NO synthesis by both the cytosolic and the particulate enzyme. These effects were partially reversed with exogenous CaM. Partial purification of the cytosolic and solubilized particulate enzymes by affinity chromatography on adenosine 2',5'-bisphosphate-Sepharose resulted in EDRF/NO synthase activities dependent on exogenous CaM. We conclude that endothelial cells contain both cytosolic and particulate enzymes that synthesize EDRF/NO. Both enzymes are regulated by free Ca2+ and, at least in part, by CaM.

Purification of a soluble isoform of guanylyl cyclase-activating-factor synthase

The soluble form of guanylyl cyclase-activating-factor (GAF) synthase from rat cerebellum was purified to homogeneity by sequential affinity chromatographic steps on adenosine 2',5'-bisphosphate (2',5'-ADP)-Sepharose and calmodulin-agarose. Enzyme activity during purification was bioassayed by the L-arginine-, NADPH-, and Ca2+/calmodulin-dependent formation of a plasma membrane-permeable nitric oxide-like factor that stimulated soluble guanylyl cyclase in RFL-6 cells. With calmodulin and NADPH as cofactors, purified soluble GAF synthase induced an increase of 1.05 mumol of cGMP per 10(6) RFL-6 cells per 3 min per mg of protein. The coproduct of this signal-transduction pathway appeared to be L-citrulline. GAF synthase catalyzed the conversion of 107 nmol of L-arginine into L-citrulline per min per mg of protein. Based on these assays, this represents a purification of GAF synthase of approximately 10,076- and 8925-fold with recoveries of 16% and 19%, respectively. Rechromatography of the purified enzyme on Mono P (isoelectric point = 6.1 +/- 0.3), Mono Q, and Superose 12 or 6 resulted in no further purification or increase in specific activity. A Stokes radius of 7.9 +/- 0.3 nm and a sedimentation coefficient s20,w of 7.8 +/- 0.2 S were used to calculate a molecular mass of about 279 +/- 25 kDa for the native enzyme. SDS/PAGE revealed a single protein band with a molecular mass of about 155 +/- 3 kDa. These data suggest that soluble GAF synthase purified from rat cerebellum is a homodimer of 155-kDa subunits and that enzyme activity is dependent upon the presence of calmodulin.

L-arginine and arginine analogues: effects on isolated blood vessels and cultured endothelial cells

1. The present study examined effects of arginine (Arg) and various Arg analogues on the vascular tone of rabbit and rat aortic rings, the release of nitrite from cultured bovine aortic endothelial cells and the metabolism of L-Arg in bovine and porcine endothelial cell homogenates. The respective D-enantiomers or N-alpha-benzoyl-L-arginine ethyl ester did not substitute for L-Arg. 2. In bovine aortic endothelial cells, the release of nitrite was only observed in the presence of L-Arg or L-Arg methyl ester in the cell culture medium. 3. In dialyzed homogenates of porcine and bovine aortic endothelial cells, L-Arg was metabolized independently of NADPH and Ca2+ to yield L-ornithine (L-Orn) and L-citrulline (L-Cit). No concomitant nitrite formation was detected. 4. Pretreatment of rabbit and rat aortic rings with L-canavanine (L-Can) or NG-monomethyl-L-Arg (L-NMMA) inhibited ATP- and acetylcholine-induced relaxations (endothelium-dependent) but not glyceryltrinitrate-induced relaxations (endothelium-independent). 5. In rabbit aortic rings, Arg and monomeric Arg analogues induced endothelium-independent relaxations. L-Arg methyl ester induced an endothelium-independent contraction, and L-NMMA induced a relaxation in the absence of endothelium and a contraction in the presence of endothelium. Polymeric basic amino acids such as poly L-Arg induced endothelium-dependent relaxations (inhibited by L-Can), a subsequent refractoriness to endothelium-dependent vasodilators (not prevented by L-Can) and endothelial cell death. 6. We suggest that extracellular L-Arg is essential for the formation of endothelium-derived nitrogen oxides (EDNO). However, Arg and Arg analogues do not exert endothelium-dependent relaxation. L-Can and L-NMMA inhibit endothelium-dependent relaxation, consistent with an inhibition of EDNO formation from L-Arg, but also exert endothelium-independent effects on vascular tone.

Basal and stimulated formation and release of L-arginine-derived nitrogen oxides from cultured endothelial cells

Endothelium-derived nitrogen oxides, i.e., nitrogen oxide and/or nitrogen oxide-containing compounds, formed from L-arginine account, at least in part, for the biological activity of endothelium-derived relaxing factor(s). We have developed a rapid and sensitive assay to determine the basal and stimulated release of defined breakdown products of endothelium-derived nitrogen oxides, i.e., nitrite and nitrate. Formation and/or release of these nitrogen oxides was time- and concentration-dependently stimulated by various endothelium-dependent vasodilators and was decreased by NG-methyl-L-arginine and L-canavanine, compounds that most likely inhibit the endothelial enzymatic conversion of L-arginine into nitrogen oxides. In addition to nitrogen oxide, hydroxylamine was shown to have pharmacological and physico-chemical properties similar to endothelium-derived relaxing factor(s). Moreover, hydroxylamine release was detected in stimulated bovine aortic endothelial cells. We suggest that hydroxylamine represents one endothelium-derived nitrogen oxide within the group of biologically active nitrogen oxides.

Hormone-induced biosynthesis of endothelium-derived relaxing factor/nitric oxide-like material in N1E-115 neuroblastoma cells requires calcium and calmodulin

Stimulation of soluble guanylyl cyclase in rat fetal lung fibroblasts (RFL-6 cells) was used as a sensitive assay for endothelium-derived relaxing factor/nitric oxide (EDRF/NO) formation. Intact N1E-115 cells released an EDRF/NO-like material that enhanced cyclic GMP levels in RFL-6 cells. The synthesis of this substance could be stimulated with the receptor agonist neurotensin (10 microM) or by addition of the EDRF/NO substrate L-arginine (100 microM). In Ca2(+)-free Locke's solution, stimulation of EDRF/NO production by both neurotensin and L-arginine was abolished. The EDRF/NO-synthesizing activity was localized in the cytosol of N1E-115 cells. The activity was lost after boiling and it was highly sensitive to Ca2+ with the major increase in activity occurring between 100 and 500 nM Ca2+. L-Arginine and NADPH were required for maximal synthesis of EDRF/NO by the enzyme(s). The synthesis of EDRF/NO was inhibited by the following antagonists of calmodulin-regulated functions (with the approximate IC50 values given in parentheses): calmidazolium (7 microM), trifluoperazine (10 microM), fendiline (80 microM), W-7 (N-[6-aminohexyl]-5-chloro-1-naphthalenesulfonamide) (120 microM), and compound 48/80 (3 micrograms/ml). The EDRF/NO-synthesizing activity was partially purified from N1E-115 cytosol by DE 52 anion exchange chromatography. The activity was eluted with 0.1 M KCl. The enzyme(s) showed very little activity in the presence of L-arginine (100 microM) and NADPH (100 microM), but the activity could be fully restored by addition of exogenous calmodulin (EC50, approximately 2 units/ml). At 0.3 M KCl, a fraction eluted from the DE 52 column that was also able to fully restore the EDRF/NO-synthesizing activity. Thus, this fraction is likely to contain the endogenous Ca2(+)-binding protein. It is concluded that the activity of the EDRF/NO-synthesizing enzyme(s) in N1E-115 neuroblastoma cells is regulated by Ca2+ and calmodulin.

Regional distribution of EDRF/NO-synthesizing enzyme(s) in rat brain

Stimulation of soluble guanylyl cyclase and increase in cyclic GMP in rat fetal lung fibroblasts (RFL-6 cells) was used as a bioassay to detect EDRF/NO formation. The cytosolic fraction of whole rat brain synthesized an EDRF/NO-like material in a process dependent on L-arginine and NADPH. The enzymatic activity was destroyed by boiling and inhibited by N omega-nitro-L-arginine. Hemoglobin and methylene blue blocked the effect of EDRF/NO. When different brain regions were analyzed in the presence of L-arginine and NADPH, the cytosolic fraction from cerebellum showed the highest EDRF/NO-forming activity (2-3 times higher than whole brain). Activity similar to whole brain was found in hypothalamus and midbrain. Enzymatic activities in striatum, hippocampus and cerebral cortex were about two thirds of whole brain. The lowest activity (less than half of whole brain) was found in the medulla oblongata.

Enzymatic formation of nitrogen oxides from L-arginine in bovine brain cytosol

In dialyzed bovine brain cytosol, the enzymatic formation of nitrogen oxides was directly determined. The basal formation of nitrite and nitrate was concentration-dependently enhanced by L-arginine (EC50 about 3.10(-5) M). Both the basal and L-arginine induced formations were inhibited by NG-monomethyl-L-arginine (EC50 about 2.10(-4) M). In the presence of L-arginine, a concomitant formation of citrulline was detected. L-Arginine methyl ester also served as a substrate, but neither D-arginine, D-arginine methyl ester nor N alpha-benzoyl-L-arginine ethyl ester did so. The formation of nitrite and nitrate was time-dependent, increased linearly with the protein concentration of the cytosol and was not observed when the cytosolic proteins were heat-denaturated. Exogenous NADPH (or NADP+) concentration-dependently enhanced the formation of nitrite and nitrate, whereas NADH, NAD+, FAD, Ca2+, Mg2+ and calmodulin were ineffective. These results indicate that bovine brain contains a cytosolic enzyme which uses NADPH or NADP+ as cofactors to form nitrogen oxides from both an endogenous non-dialyzable substrate and from L-arginine.

Formation and release of nitric oxide from human neutrophils and HL-60 cells induced by a chemotactic peptide, platelet activating factor and leukotriene B4

Vascular endothelial cells and neutrophils synthesize and release potent vasodilatatory factors, i.e. endothelium-derived relaxing factors (EDRF) and neutrophil-derived relaxing factors (NDRF). One EDRF has been identified as nitric oxide (NO) derived from arginine. We studied the synthesis and release of NO from human neutrophils stimulated with the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine, platelet activating factor or leukotriene B4. The formation and release of NO was enhanced several-fold in the presence of superoxide dismutase, probably by inhibiting superoxide-induced breakdown of NO. The formation and release of NO but not the formation of superoxide anions was decreased in neutrophils pretreated with L-canavanine, an inhibitor of arginine-utilizing enzymes. Our data suggest that at least one NDRF is identical with NO or another labile NO containing compound derived from arginine.

[Clinical aspects and functional diagnostic findings of Takayasu disease]

Aetiopathogenesis, clinical picture, laboratorical and functional diagnostic methods of ten patients suffering from Takayasu's arteritis out of 1164 patients suspicious of cerebrovascular insufficiency are described. The combined use of Dopplersonography, ophthalmodynamometry and ophthalmodynamography permit in all cases the assessment of vascular pathology in supraaortic arteries. The specific diagnosis was made in connection which clinical, anamnestical and paraclinical findings. There are some characteristic functional diagnostic results in Takayasu's arteritis. The noninvasive diagnostic methods are useful tools to estimate the progredience of this disease in his chronical course.

Arginine is a physiological precursor of endothelium-derived nitric oxide

ATP dose dependently stimulated the formation and release of nitric oxide (NO) from perfused rabbit aorta. L-Canavanine, an inhibitor of various L-arginine-utilizing enzymes, abolished basal and ATP-induced NO formation and release. ATP increased the accumulation of presumably NO-derived NO2- in the medium of primary cultures of bovine aortic endothelial cells. 15NO, 15NO2- and 15NO3- formation was found when L-[guanido-15N2]arginine was added to the culture medium. We conclude that the terminal guanidino nitrogens of L-arginine are the physiological precursors of endothelium-derived NO.

[Ambulatory physical therapy rehabilitation with interval walking-gymnastics therapy in patients with chronic peripheral arterial occlusive disease]

A ambulatory physical therapeutic rehabilitation by means of interval-run-gymnastic-therapy was examined by a prospective study of 43 patients with peripheral arterial disease of the legs and was estimated as practicable. Improvements of walk distance, lengthenings of the pain times in the standardized move up and down-test, decreases of the blood-pressure gradients by ultrasonic Doppler measurements, shortenings of the half-life periods of xenon-clearance, improvements of the metabolism of lactate, improvements of the parameter of metabolism of lipids and uric acid were proved. Successes of therapy were not proved by oscillography and venous occlusion plethysmography. The expense was registered by the loss of working time and discussed.

[Behavior of blood pressure and peripheral hemodynamics in interval therapy in untreated and propranolol-treated patients with arterial circulatory disorders of the lower extremities]

Searching for a possibility of an effective therapy of disturbances of peripheral arterial blood supply (stage I and II), the authors examined a medicamentously untreated group of patients as well as a comparable group of patients which was pretreated with propranolol. The two groups of patients performed twice a week an interval run exercise. Under the three-month training therapy in the two groups significant systolic and diastolic blood pressure reductions as well as statistically ascertained shortenings of the xenon-133-half-value time under working conditions and enlargements of the average functional vascular cross section A appeared. The distance of the intermittent claudication and the standardized moving up and down test prolonged. An influence on the microcirculation caused by propranolol could not be proved. The results are discussed on the basis of literature.

Local modulation of noradrenaline release in vivo: presynaptic beta 2-adrenoceptors and endogenous adrenaline

Isoprenaline bitartrate (0.5 microgram/kg/min i.v.) increased the rate of noradrenaline release into the circulation of pentobarbitone-anesthetized rabbits. This increase was much greater than that produced by an equi-hypotensive dose of the vasodilator hydralazine (0.2 mg/kg i.v.), suggesting that it was only partly due to baro-reflex activation of sympathetic nerves. This facilitatory effect of isoprenaline was also observed in the nephrectomized, pithed rabbit, with electrically stimulated sympathetic outflow, ruling out central nervous system and renin-angiotensin effects. ICI 118,551 HCl (0.3 mg/kg + 0.1 mg/kg/h i.v.) blocked the isoprenaline-induced hypotension, but did not affect the isoprenaline-induced tachycardia, suggesting that it selectively blocked beta 2-adrenoceptors. ICI 118,551 totally abolished the isoprenaline-induced increase in noradrenaline release, suggesting a beta 2-effect. Atenolol (0.3 mg/kg + 0.1 mg/kg/h) blocked the isoprenaline-induced tachycardia, a beta 1-effect, but only slightly attenuated the isoprenaline-induced increase in noradrenaline release. Atenolol by itself decreased heart rate and arterial pressure, but there was no reflex rise in the noradrenaline release rate, which suggests that atenolol impairs baroreceptor activation of sympathetic nerves. In another series of experiments, also in the pentobarbitone-anesthetized rabbit, adrenaline was released into the circulation by splanchnic nerve stimulation. This resulted in prolonged increases of adrenaline levels in heart tissue. After the plasma adrenaline levels had returned to prestimulation values, the rate of noradrenaline release into the plasma was enhanced. This increase was not observed in rabbits treated with either desipramine HCl (1 mg/kg i.v.) or propranolol HCl (2 mg/kg i.p.).(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of a 3-month-interval running exercise in combination with vasodilative therapy on microcirculation of the lower leg in peripheral arterial circulation disorders (stage I and II)]

The authors report results of a three-month-interval running exercise under continuous vasodilatory therapy (Radecol and Jupal) in cases of peripheral arterial blood disturbances (stage I and II). Apart from control examination with the whipping test, the ultra-sound-Doppler method, phlebemphraxis-plethysmography, the paper reports above all the effects of interval running on the peripheral microcirculation of the working muscles which were determined by means of Xenon-133-clearance-half-life. Independent of the type of drug therapy used, significant (1 per cent) improvements of peripheral haemodynamics were found regarding the therapeutic regime presented.

[Experiences with the application of physiotherapy in peripheral arterial circulatory disorders of the lower extremities (stage I and IIa) under ambulatory conditions]

In a comparative study the authors report on results of series of physical therapy in disturbances of the peripheral arterial blood supply. Examined were the behaviour of blood pressure, the painless walking distance and the peripheral microcirculation with the xenon-133-muscle clearance method before and after treatments lasting 10 to 12 weeks with combined exercises consisting of gymnastics and walking according to the interval principle (twice a week), with sauna visits twice a week as well as before and after diadynamic series of the current. In all therapy groups an improvement of the peripheral haemodynamics could be statistically ascertained. The distance of the intermittent claudication prolonged particularly in the group with interval walking. In the walking group and in the sauna group the values of the systolic blood pressure were significantly reduced. Side-effects were not observed. Therapy effects of the series of physical therapy described are best to be proved by the xenon-133 muscle clearance.