A Novel Class of Herbicides (Specific Inhibitors of Imidazoleglycerol Phosphate Dehydratase)

A new mode of herbicidal action was established by finding specific inhibitors of imidazoleglycerol phosphate dehydratase, an enzyme of histidine (His) biosynthesis. Three triazole phosphonates inhibited the reaction of the enzyme with Ki values of 40 [plus or minus] 6.5, 10 [plus or minus] 1.6, and 8.5 [plus or minus] 1.4 nM, respectively, and were highly cytotoxic to cultured plant cells. This effect was completely reversed by the addition of His, proving that the cytotoxicity was primarily caused by the inhibition of His biosynthesis. These inhibitors showed wide-spectrum, postemergent herbicidal activity at application rates ranging from 0.05 to 2 kg/ha.

Analysis of IL-2 gene regulation in c-fos transgenic mice. Evidence for an enhancement of IL-2 expression in splenic T cells stimulated via TCR/CD3 complex

Effects of the deregulated c-fos gene product on IL-2 expression were studied in splenic T cells from c-fos transgenic (H2-c-fos) mice. IL-2 gene expression and IL-2 production by H2-c-fos T cells stimulated with immobilized anti-CD3 Abs were enhanced and prolonged as compared with those by control T cells. Activator protein-1 activity in nuclear extract from the H2-c-fos T cells was also higher than that from the control cells. There was no significant difference in the activity of other transcription factors including IL-2 kappa B, NFAT, and Oct-1, between the H2-c-fos and the control T cells. However, activity of a negative regulatory element binding factor (NRE-A) in the H2-c-fos T cells was much lower than that in the control cells. These results suggest that c-Fos/activator protein-1 is a major regulatory factor for IL-2 gene expression in splenic T cells activated through the TCR/CD3 complex.

Analysis of IL-2 gene regulation in c-fos transgenic mice. Evidence for an enhancement of IL-2 expression in splenic T cells stimulated via TCR/CD3 complex

Effects of the deregulated c-fos gene product on IL-2 expression were studied in splenic T cells from c-fos transgenic (H2-c-fos) mice. IL-2 gene expression and IL-2 production by H2-c-fos T cells stimulated with immobilized anti-CD3 Abs were enhanced and prolonged as compared with those by control T cells. Activator protein-1 activity in nuclear extract from the H2-c-fos T cells was also higher than that from the control cells. There was no significant difference in the activity of other transcription factors including IL-2 kappa B, NFAT, and Oct-1, between the H2-c-fos and the control T cells. However, activity of a negative regulatory element binding factor (NRE-A) in the H2-c-fos T cells was much lower than that in the control cells. These results suggest that c-Fos/activator protein-1 is a major regulatory factor for IL-2 gene expression in splenic T cells activated through the TCR/CD3 complex.

[Quantifying regional cerebral blood flow with N-isopropyl-p-[123I]iodoamphetamine and SPECT by one-point sampling method]

We developed a new non-invasive technique; one-point sampling method, for quantitative measurement of regional cerebral blood flow (rCBF) with N-isopropyl-p-[123I]iodoamphetamine and SPECT. Although the continuous withdrawal of arterial blood and octanol treatment of the blood are required in the conventional microsphere method, the new technique does not require these two procedures. The total activity of 123I-IMP obtained by the continuous withdrawal of arterial blood is inferred by the activity of 123I-IMP obtained by the one point arterial sample using a regression line. To determine when one point sampling time was optimum for inferring integral input function of the continuous withdrawal and whether the treatment of sampled blood for octanol fraction was required, we examined a correlation between the total activity of arterial blood withdrawn from 0 to 5 min after the injection and the activity of one point sample obtained at time t, and calculated a regression line. As the results, the minimum % error for the inference using the regression line was obtained at 6 min after the 123I-IMP injection, moreover, the octanol treatment was not required. Then examining an effect on the values of rCBF when the sampling time was deviated from 6 min, we could correct the values in approximately 3% error when the sample was obtained at 6 +/- 1 min after the injection. The one-point sampling method provides accurate and relatively non-invasive measurement of rCBF without octanol extraction of arterial blood.

Glu318 and Thr319 mutations of cytochrome P450 1A2 remarkably enhance homolytic O-O cleavage of alkyl hydroperoxides. An optical absorption spectral study

Interactions of putative distal mutants of cytochrome P450 1A2 (P450 1A2) with hydroperoxides were studied with optical absorption spectroscopy. The Soret absorption at 393 nm of the wild-type P450 1A2 decreased by adding H2O2, tert-butyl hydroperoxide (TBHP), and cumyl hydroperoxide (CHP), whereas the absorption decrease was accompanied by the appearance of a new band around 423 nm for Glu318 and Thr319 mutants with similar treatments. Spectral simulation based on Gaussian analyses and visible bands indicate that H2O2- and TBHP-induced intermediates' spectra of the wild type are close to that of Compound I of horseradish peroxidase, whereas TBHP- and CHP-induced intermediates' spectra of the mutants are close to that of Compound II of horseradish peroxidase. Based on kinetic parameters of the spectral changes, it is suggested that: 1) TBHP and CHP mainly form porphyrin+.FeIV = O due to heterolytic O-O scission in the wild type, while forming porphyrinFeIV = O for the mutants owing to homolytic O-O scission; and 2) heterolytic O-O scission of H2O2 is not changed by the mutations. Heterolytic/homolytic cleavage ratios for the P450 1A2 reactions with CHP obtained from product analysis were consistent with those obtained from spectral changes.

Essential role of His163 of cytochrome P450 1A2 in catalytic functions associated with cytochrome b5

The effect of cytochrome b5 on the activity of cytochrome P450 1A2 (P450 1A2) and three site-directed mutants designed to alter surface charges has been investigated. Cytochrome b5 increased the rate of oxidation of methanol and/or 7-ethoxycoumarin 2- to 10-fold in both wild type and mutant P450. Cytochrome b5 also increased the coupling of electron transfer to substrate hydroxylation as opposed to the uncoupling reaction which leads to peroxide production. The effect of cytochrome b5 on both wild type and the Lys99Glu and Lys401Glu mutants are similar. In contrast, turnover numbers in the His163Glu mutant did not change in the presence of cytochrome b5. The reduction potential of the His163Glu mutant decreased approximately -40 mV while the Lys99Glu and Lys401Glu mutants exhibited little change. The rate of photoreduction decreased from 1.1 x 10(-1) min-1 to 8.3 x 10(-3) min-1 in the His163Glu mutant while the rate of electron transfer from ferrous P450 to ferric cytochrome b5 increased from 0.02 min-1 to > 5 min-1. Overall, the present study suggests that His163 is important to keep an appropriate redox potential of P450 1A2 for optimum electron transfer to occur from cytochrome b5. Based on the P450 101 crystal structure, His163 is not expected to directly contact the heme. Therefore, the resulting change in redox properties in the His163Glu mutant is probably not the result of a direct electrostatic change in the heme environment.

Differential roles of Glu318 and Thr319 in cytochrome P450 1A2 catalysis supported by NADPH-cytochrome P450 reductase and tert-butyl hydroperoxide

The kinetic values for 7-ethoxycoumarin (7-EC) hydroxylation have been obtained in both the NADPH-cytochrome P450 reductase- and tert-butyl hydroperoxide (TBHP)-supported systems for several Glu318 and Thr319 mutants of cytochrome P450 1A2. The results with the reductase-supported system suggest that Glu318 is important for both substrate binding and catalysis, whereas Thr319 is critical for neither, although the size of the residue at position 319 influences catalytic activity. In contrast, neither Glu318 nor Thr319 appears to be important for catalytic turnover in the TBHP-supported system despite the fact that the size of the amino acid at position 319 affects the binding of TBHP and 7-EC in opposite manners. The roles of these two distal amino acids in the cytochrome P450 1A2-catalyzed oxidation of 7-EC therefore differ for the reactions supported by cytochrome P450 reductase and TBHP.

[A problem of quantitative measurement of regional cerebral blood flow using microsphere model and N-isopropyl-p-[123I]iodoamphetamine (IMP): comparison with 133Xe SPECT and sequential dynamic 123I-IMP SPECT]

Regional cerebral blood flow (rCBF) was measured in 13 patients with various cerebral disease by N-isopropyl-p-[123I]iodoamphetamine (IMP) SPECT with the microsphere model (rCBF (CbST)), which was compared with 133Xe inhalation SPECT (rCBFXe). Continuous withdrawal of arterial blood was performed for 5 minutes and SPECT image was obtained from 25 min to 55 min after the tracer injection. The reconstructed counts at 5 min was corrected using entire cerebral counts collected at 5 min, 20 min, and 60 min after the tracer injection. As compared with rCBFXe, rCBF (CbST) was underestimated in high flow areas and overestimated in low flow areas. Regional CBF was also measured using one minute short time SPECT images at 5 min (rCBF (Cb5)), 20 min (rCBF (Cb20)), and 60 min (rCBF (Cb60)) after the injection. Regional CBF tended to be underestimated with time from the tracer injection due to the wash-out from brain tissue to blood. In comparison with rCBF (Cb5), rCBF (CbST) was underestimated in high flow areas and overestimated in low flow areas. This error was considered to be due to the correction of reconstruct counts using entire cerebral counts, because of the kinetic behavior of 123I-IMP was different in each region of the brain.

Purification and Properties of a Monofunctional Imidazoleglycerol-Phosphate Dehydratase from Wheat

Imidazoleglycerol-phosphate dehydratase (EC 4.2.1.19) activity was detected in extracts of several monocotyledonous and dicotyledonous plants using a newly developed assay method. The enzyme was purified 114,000-fold (to apparent homogeneity) from wheat germ by five chromatographic steps. Its native relative molecular weight (Mr) was determined to be 600,000 to 670,000, and it consists of identical subunits of Mr 25,500. In wheat germ, the dehydratase, unlike those of prokaryotic origin, is not associated with histidinol phosphatase activity. The reaction product was identified as imidazoleacetol phosphate (IAP) by comparing it with synthetic IAP as an authentic reference. The Km value for imidazoleglycerol phosphate was 0.36 mM at the optimal pH of 6.6. The enzyme required a reducing agent, such as 2-mercaptoethanol or dithiothreitol, and Mn2+ for maximal activity. 3-Amino-1,2,4-triazole competitively inhibited the activity with a Ki value of 46 [mu]M. The purification of imidazoleglycerol-phosphate dehydratase from wheat germ and histidinol dehydrogenase from cabbage (A. Nagai, A. Scheidegger [1991] Arch Biochem Biophys 284: 127-132) suggests that at least the second half of the histidine biosynthesis in plants is identical to that in microorganisms.

[A new graphic method for evaluation of distribution volume on N-isopropyl-p-[123I]iodoamphetamine (IMP) SPECT]

We developed a new graphic method using N-isopropyl-p-[123I]iodoamphetamine (IMP) and SPECT of the brain, the graph on which all three parameters, cerebral blood flow, distribution volume (Vd) and delayed count to early count ratio (Delayed/Early ratio), were able to be evaluated simultaneously. The kinetics of 123I-IMP in the brain was analyzed by a 2-compartment model, and a standard input function was prepared by averaging the time activity curves of 123I-IMP in arterial blood on 6 patients with small cerebral infarction etc. including 2 normal controls. Being applied this method to the differential diagnosis between Parkinson's disease and progressive supranuclear palsy, we were able to differentiate both with a glance, because the distribution volume of the frontal lobe significantly decreased in Parkinson's disease (Mean +/- SD; 26 +/- 6 ml/g). This method was clinically useful. We think that the distribution volume of 123I-IMP may reflect its retention mechanism in the brain, and the values are related to amine, especially to dopamine receptors and its metabolism.

Effect of mutations of ionic amino acids of cytochrome P450 1A2 on catalytic activities toward 7-ethoxycoumarin and methanol

Catalytic efficiencies, percentages of rates of product formation per NADPH oxidized, and rates of product formation per O2 consumed of ionic mutants of cytochrome P450 1A2 (P450 1A2) were studied. Efficiencies of Lys99Glu, Lys453Glu, and Arg455Glu mutants for the hydroxylation reaction toward 7-ethoxycoumarin in the reconstituted system were much lower than that of the wild type (less than 17%), which corresponds to lower turnover numbers for these mutants. In contrast, the catalytic efficiencies for the hydroxylation reaction toward methanol of the three mutants were more than 45% that of the wild type in spite of these mutants' lower turnover numbers. Turnover numbers and catalytic efficiencies of Arg137Leu and Lys401 Glu mutants toward both substrates were comparable to those of the wild type. The electron-transfer rate from the reductase to the heme of P450 1A2 was decreased by 30% upon addition of excess methanol, while it was not influenced by addition of excess 7-ethoxycoumarin. The turnover numbers toward both 7-ethoxycoumarin and methanol as well as the rate constant of electron transfer were decreased by 25-40% by raising the concentration of KCl from 0 to 300 mM in the reconstituted system containing 50 mM potassium phosphate buffer. The turnover numbers toward both substrates of the above-mentioned five ionic mutants caused by tert-butyl hydroperoxide in the absence of the reductase and NADPH were comparable to those of the wild type. The effect of phospholipid constituents on the catalytic activity toward 7-ethoxycoumarin of the wild type was also studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of class II MHC gene expression by the inducible anti-sense RNA in transgenic mice

We have established a gene regulatory system in mice by the inducible anti-sense RNA. We have generated transgenic mice carrying the anti-sense DNA composed of the class II MHC gene under the control of the human metallothionein IIa gene promoter. The detectable amount of anti-sense RNA was constitutively produced in spleen and bone marrow from transgenic mice and the amount in spleen was increased about fivefold by the stimulation of mice with heavy metal ions. We have previously reported that the reduction of class II MHC molecules on early B lineage cells by the anti-sense RNA results in delay of their development in the bone marrow culture. The early B cell development was slightly delayed in the culture from the transgenic mice. This delay was augmented in the culture by the addition of heavy metal ions in proportion to its concentration. These results suggest that the inducible anti-sense RNA reduces the expression of class II MHC molecules on B lineage cells.

A case complicated with SLE during maintenance hemodialysis

A 40-year-old woman suffered from toxemia of pregnancy in 1977 and was admitted to hospital. Thereafter, she developed nephrotic syndrome, underwent a renal biopsy, and a diagnosis of membranoproliferative glomerulonephritis (MPGN) was made. She received steroid therapy, immunosuppressive drug and anticoagulant therapy, and recovered sufficiently to be discharged from hospital in April, 1979. During subsequent ambulatory treatment at our outpatient department, her renal function deteriorated gradually, and maintenance hemodialysis was started from June, 1990. In July, 1991, she was admitted to our hospital with pleurisy and pericarditis. There was no improvement despite antibiotic treatments. Laboratory data revealed leukopenia and lymphopenia. Under suspicion of systemic lupus erythematosus (SLE), relevant tests were carried out. Immunological abnormalities such as positive LE cells and the presence of various autoantibodies, together with clinical signs of hypersensitivity to sunlight, stomatitis and serositis, satisfied the diagnostic criteria of the ARA and a diagnosis of SLE was made. This case did not exhibit any clinical or serological abnormalities except for the renal disorder for a 10-year period after the histological diagnosis of MPGN, but was eventually diagnosed as SLE as a result of the manifestation of SLE symptoms for the first time after one year of maintenance hemodialysis. Immunological abnormalities and SLE during maintenance hemodialysis are discussed in relation to other reports.

The cytochrome P450 1A2 active site: topology and perturbations caused by glutamic acid-318 and threonine-319 mutations

Phenyldiazene reacts with rat liver CYP1A2 expressed in Saccharomyces cerevisiae to give a phenyl-iron complex that rearranges to a mixture (NB:NA:NC:ND = 12:54:14:20, subscript indicates pyrrole ring) of N-phenyl-PPIX (PPIX = protoporphyrin) regioisomers. The same isomer pattern is obtained in each instance when the purified or microsomal enzyme reacts with phenyldiazene, indicating that the active site topology is not altered by removal of the protein from the membrane. Reaction of the enzyme with biphenylhydrazine gives a similar distribution of N-biphenyl-PPIX isomers, but reaction with (2-naphthyl)-hydrazine only gives the NC and ND regioisomers and a trace of the NA isomer of N-(2-naphthyl)-PPIX. The mutations E318D, E318A, and E318V cause relatively minor changes in the observed regioisomer ratios. In contrast, the mutations T319A, T319V, and T319S suppress formation of the NC and ND isomers of N-phenyl-PPIX. The reaction of T319A with biphenylhydrazine yields major amounts of the NB adduct rather than the small amounts observed with CYP1A2 and the Glu-318 mutants, but does not give the NC and ND regioisomers. Other, less dramatic, changes in the isomer ratios are also observed. The results indicate that the active site of CYP1A2 is open above all four quadrants of the heme group including, to some extent, the region above pyrrole ring B. Pyrrole ring B is completely inaccessible in most cytochrome P450 enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Chiral recognition at cytochrome P450 1A2 active site: effects of mutations at the putative distal site on the bindings of asymmetrical axial ligands

Effects of mutations at the putative distal site of cytochrome P450 1A2 on chiral discrimination for binding (R)-(+)- and (S)-(-)-1-(1-naphthyl)ethylamine (ligand I), (R)-(-)- and (S)-(+)-1-cyclohexylethylamine (ligand II), and (R)-(+)- and (S)-(-)-1-(4-pyridyl)ethanol (ligand III) were studied by optical absorption spectra. The wild-type P450 1A2 exhibited different dissociation constants (Kd) for the R- and S-enantiomers of these ligands. The R/S ratios of the Kd values for ligands I and II were 5.2 and 2.9, respectively, and the S/R ratio for ligand III was 6.0. Mutations at the putative distal site, such as Glu318Asp and Glu318Ala, remarkably enhanced the discrimination: the R/S ratio of the Kd values for ligand I increased from 5.2 to 20-60, while the R/S ratio for ligand II decreased from 2.9 to 0.8-0.9. These remarkable changes in the R/S ratios were not observed with Glu318Asp mutation for ligand III binding, whereas affinities for both enantiomers of ligand III were markedly decreased by the Glu318Ala mutation. Mutation Thr319Ala increased the R/S ratio of the Kd values for ligand I slightly but markedly decreased the R/S ratio of ligand II (from 2.9 to 0.8) and the S/R ratio of ligand III (from 6.0 to 1.0). Similar enhancements of the chiral discriminations were observed with the mutation Lys250Leu at another putative substrate-recognition site. Differences between the R- and S-enantiomers of the standard enthalpy and entropy of ligand III binding were changed most remarkably by the Thr319Ser mutation.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatocyte growth factor down-regulates the alpha-fetoprotein gene expression in PLC/PRF/5 human hepatoma cells

Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes; however, in certain human hepatoma cell lines, the growth is inhibited by HGF. In the present study, the effect of HGF on the alpha-fetoprotein (AFP) gene expression was analyzed in PLC/PRF/5 human hepatoma cells. HGF did not inhibit cell proliferation, but dose-dependently suppressed AFP secretion at the concentrations of 10 ng/ml or less. By Northern blot analysis, the levels of AFP mRNA were suppressed by HGF, whereas the levels of beta-actin mRNA used as a control did not show any significant changes. In the transient chloramphenicol acetyltransferase plasmid transfection assays, the AFP promoter activity was repressed by HGF, in contrast, the AFP enhancer activity was not affected by HGF. These results suggest that the AFP gene expression is down-regulated by HGF through the suppression of its promoter activity in human hepatoma cells.

Binding study of metal ions to S100 protein: 43Ca, 25Mg, 67Zn and 39K n.m.r

The interactions of the S100 protein (S100) with metal cations such as Ca2+, Mg2+, Zn2+ and K+ were studied by the metal n.m.r. spectroscopy. The line widths of 43Ca, 25Mg, 67Zn and 39K n.m.r. markedly increased by adding all S100s. A broad 43Ca n.m.r. band of Ca(2+)-S100a solution was not affected by Zn2+ and K+, while it was greatly decreased by adding Mg2+. The 43Ca n.m.r. spectra of Ca(2+)-S100a0 and -S100b solutions consisted of two slow-exchangeable signals which corresponded to Ca2+ bound to two environmentally different sites of the S100a0. These two 43Ca n.m.r. signals were not affected by Zn2+ and K+. The line width of broad 25Mg n.m.r. band of the Mg(2+)-S100 solution greatly decreased by adding Ca2+, while it did not change by adding Zn2+ and K+. Further, the addition of Ca2+, Mg2+ and K+ did not affect the line width of the 67Zn n.m.r. of the Zn(2+)-S100 solutions. These findings suggest that: (1) Mg2+ binds to all S100s, and at least one of the Mg2+ binding sites of S100 molecule is the same as the Ca2+ binding site; (2) Zn2+ binds to S100s, although the binding site(s) is/are different from Ca(2+)- or Mg(2+)-binding site(s), and the environment of Zn2+ nuclei will not change even though Ca2+ binds to S100s.

Putrescine N-Methyltransferase in Cultured Roots of Hyoscyamus albus: n-Butylamine as a Potent Inhibitor of the Transferase both in Vitro and in Vivo

Biosynthesis of tropane alkaloids is thought to proceed by way of the diamine putrescine, followed by its methylation by putrescine N-methyltransferase (PMT; EC 2.1.1.53). High PMT activities were found in branch roots and/or cultured roots of several solanaceous plants. PMT was partially purified and characterized from cultured roots of Hyoscyamus albus that contain hyoscyamine as the main alkaloid. Initial velocity studies and product inhibition patterns of PMT are consistent with an ordered bi-bi mechanism, in which the K(m) values for putrescine and S-adenosyl-l-methionine are 277 and 203 mum, respectively, and the K(i) value for S-adenosyl-l-homocysteine is 110 mum. PMT efficiently N-methylated amines that have at least two amino groups separated by three or four methylene groups. Monoamines were good competitive inhibitors of PMT, among which n-butylamine, cyclohexylamine, and exo-2-aminonorbornane were most inhibitory, with respective K(i) values of 11.0, 9.1, and 10.0 mum. When n-butylamine was fed to root cultures of H. albus, the alkamine intermediates (tropinone, tropine, and pseudotropine) drastically decreased at 1 mm of the exogenous monoamine, and the hyoscyamine content decreased by 52% at 6 mm, whereas the contents of 6beta-hydroxyhyoscyamine and scopolamine did not change. Free and conjugated forms of polyamines were also measured. The n-butylamine treatment caused a large increase in the putrescine content (especially in the conjugated pool), and the spermine content also increased slightly, whereas the spermidine content decreased slightly. The increase in the putrescine pool size (approximately 40 nmol/mg dry weight) was large enough to account for the decrease in the total alkaloid pool size. Similar results were also obtained in root cultures of Datura stramonium. These studies further support the role of PMT as the first committed enzyme specific to alkaloid biosynthesis.

Effect of mutations at Lys250, Arg251, and Lys253 of cytochrome P450 1A2 on the catalytic activities and the bindings of bifunctional axial ligands

Some eukaryotic cytochromes P450 (P450s) have a series of ionic amino acids, corresponding to Lys250, Arg251, and Lys253 residues in the P450 1A2 sequence. To understand the roles of those ionic amino acids in the catalytic function of P450, three single mutants, Lys250Leu, Arg251Leu, and Lys253Leu of P450 1A2 were obtained from yeast (Saccharomyces cerevisiae) expression system. Turnover numbers of the Arg251Leu mutant in dealkylation reactions of methoxy- and ethoxyresorufin catalyzed by the P450 reconstituted system were remarkably increased by sixfold compared to those of the wild type. The Lys250Leu and Lys253Leu mutants also showed turnover numbers higher than those of the wild type by three- to fourfold. Those catalytic activities were inhibited competitively by pyridine derivatives, nitrogenous axial ligands to the P450 heme. From those findings together with other spectral data, it was suggested that the ionic site of Lys250, Arg251, and Lys253 may be somehow located near the substrate recognition site and/or near the axial-ligand access channel of this enzyme.

Role of I-A molecules in early stages of B cell maturation

The role of the Ia molecule in the early phase of B cell development remains controversial. In contrast to previous studies, we have detected minute amounts of Ia (I-A) molecule on early B lineage (B220+IgM-) cells from normal bone marrow, using ELISA. The presence of the I-A molecule even on pro-B cells was deduced from experiments in which a monoclonal anti-I-A antibody completely blocked the generation of pre-B cells from B progenitor (B220-) cells in stromal cell-dependent B cell culture. Inasmuch as this antibody did not inhibit the maturation of pre-B cells to IgM+ B cells in culture, the I-A molecule on early B lineage cells probably plays a role in their maturation. We also examined the role of the I-A molecule in early B cell development, using transgenic mice harboring the antisense DNA to I-A beta-chain gene. The amount of I-A molecule on splenic B cells from the young transgenic mice decreased in the presence of abundant amounts of the antisense RNA. B cell development was perturbed in spleen from the transgenic mice. Stromal cell-dependent B cell cultures from these mice clearly showed that the maturation of B lineage cells was delayed at a very early stage of development (B220- to B220+). We propose that the I-A molecule on early B lineage cells may play an essential role in their maturation.

Role of I-A molecules in early stages of B cell maturation

The role of the Ia molecule in the early phase of B cell development remains controversial. In contrast to previous studies, we have detected minute amounts of Ia (I-A) molecule on early B lineage (B220+IgM-) cells from normal bone marrow, using ELISA. The presence of the I-A molecule even on pro-B cells was deduced from experiments in which a monoclonal anti-I-A antibody completely blocked the generation of pre-B cells from B progenitor (B220-) cells in stromal cell-dependent B cell culture. Inasmuch as this antibody did not inhibit the maturation of pre-B cells to IgM+ B cells in culture, the I-A molecule on early B lineage cells probably plays a role in their maturation. We also examined the role of the I-A molecule in early B cell development, using transgenic mice harboring the antisense DNA to I-A beta-chain gene. The amount of I-A molecule on splenic B cells from the young transgenic mice decreased in the presence of abundant amounts of the antisense RNA. B cell development was perturbed in spleen from the transgenic mice. Stromal cell-dependent B cell cultures from these mice clearly showed that the maturation of B lineage cells was delayed at a very early stage of development (B220- to B220+). We propose that the I-A molecule on early B lineage cells may play an essential role in their maturation.

Accelerated decay of the cell bound C4b2a complex by serum of patients with membranoproliferative glomerulonephritis and acute poststreptococcal glomerulonephritis

Serum from patients with membranoproliferative glomerulonephritis (MPGN) and acute poststreptococcal glomerulonephritis (APSGN) accelerated the decay of the cell bound C4b2a (C42) and C4b hemolytic activity relative to pooled normal human serum (pNHS) after 5 min incubation at 30 degrees C in EDTA-GVB. The accelerated decay of the C42 hemolytic activity was heat stable (56 degrees C 30 min) and was inhibited by monoclonal antibody against human C4 binding protein (MoAb:C4BP) or C4 binding protein (C4BP) depleted serum. C4 nephritic factor (C4NeF) was employed to stabilize the labile classical pathway C3 convertase C42 complex. Serum from patients with MPGN and APSGN reduced the C4NeF stabilizing activity. Sera from 32 of 46 patients with MPGN and all of 7 patients with APSGN reduced the C42 hemolytic activity relative to 50 normal human serum (NHS) after 5 min incubation at 30 degrees C in EDTA-GVB, and there was no relationship with the serum concentration of C4BP. In vivo, accelerated decay of C42 convertase might interfere with the clearing and processing mechanism of circulating immune complexes (IC) by reducing deposition of C3b on the IC lattice.

[Relationship between types of hypertension and patterns of urinary catecholamine excretion in Sipple's syndrome]

We report here a case of Sipple's syndrome, and we also analyze the relationship between the type of hypertension and urinary excretion of catecholamines in Sipple's syndrome based on the literature in Japan. One hundred and fourteen cases of Sipple's syndrome have been reported in Japan. The hypertension of patients with Sipple's syndrome shows a ratio of fitfull hypertension to continual hypertension of 6 to 1, whereas the ratio is 1 to 1.5 in patients whose pheochromocytoma is not accompanied by Sipple's syndrome. The patients with Sipple's syndrome, being pheochromocytoma can be classified into the adrenaline (U-AD) dominant type and noradrenaline (U-NA) dominant type based on the catecholamine excretion in the urine. The U-AD predominant (U-AD/U-NA greater than 0.4) patients mostly reveal fitfull hypertension, while patients with continual hypertension hardly show U-AD predominant.

Role of Glu318 and Thr319 in the catalytic function of cytochrome P450 d (P4501A2): effects of mutations on the methanol hydroxylation

Polar amino acids in the (putative) distal site are well conserved in P450s. For example, Glu318 for P450d is well conserved as either Glu or Asp for P450s, and Thr319 for P450d is also conserved for P450s. We have studied how mutations at Glu318 and Thr319 of P450d influence the catalytic activity toward methanol associated with the activation of O2. Catalytic activities of Glu318Asp, Glu318Ala, and Thr319Ala mutants toward methanol were 60, 25, and 38%, respectively, compared with that of the wild type. O2 consumption and NADPH oxidation rates of each mutants varied corresponding to the catalytic activities. However, surprisingly, efficiency (16-40%) of incorporated O to the substrate vs. consumed O2 for the Glu318Ala and Thr319Ala mutants were higher than that (9%) of the wild type. In addition, H2O2, which is produced from uncoupling for the wild-type P450d, was not observed for reaction of the Glu318Ala and Thr319Ala mutants. It seemed that consumed O2 was partially reduced to 2 mol of H2O by 4-electron transfer from NADPH for the wild-type and Thr319Ala mutant. However, for the two Glu318 mutants, it appeared that the consumed O2 was not reduced in the same way. It was thus suggested that the conserved Glu318 and Thr319 of P450d are not essential for the activation of O2 in the methanol oxidation. Role of the water molecule or the methanol molecule in the catalytic function was implied.

Early morphological changes of tubules in rats with chronic renal failure

We investigated the early changes of tubules and effect of the oral adsorbent, AST-120, on the early changes of tubules in rats with chronic renal failure. Sprague-Dawley rats were divided into two groups with and without AST-120, after 3/4 nephrectomy. Although there were no significant differences in levels of blood urea nitrogen, serum creatinine, creatinine clearance, inulin clearance, para-aminohippuric acid clearance and urinary N-acetyl-beta-D-glucosaminidase at week 8 between the two groups, the amount of 24-hour urinary protein excretion and the direct systolic blood pressure at week 8 were significantly decreased in the group with AST-120. Examinations by light microscopy at week 8 revealed that proteinaceous casts in the tubules, tubular dilatation and infiltration of monocytes into the interstitium in the group with AST-120 were less prominent than those in the group without AST-120. A significant difference in numbers of proteinaceous casts was noted at week 8 between the two groups. In rats with chronic renal failure at the early stage, it is concluded that the formation of proteinaceous casts, resulting in tubular damage, is increased and that AST-120 delays the occurrence of proteinaceous casts by delaying the increase in urinary protein excretion.

Effects of L-NG-monomethyl arginine on the cyclic GMP formations in rat mesenteric arteries

To evaluate the contribution of L-arginine as a precursor of the endothelium-derived relaxing factor (EDRF) on vascular cyclic GMP formation, we examined the effects of L-NG-monomethyl arginine (L-NMMA), and analog of L-arginine, on basal and acetylcholine (ACh)-, sodium nitroprusside (SNP)- and atrial natriuretic peptide (ANP)-induced cyclic GMP formations in rat mesenteric arteries. The mesenteric arteries were perfused with Krebs-Henseleit solution containing 0.2 mM isobutyl methyl xanthine. The effluents from the arteries were collected before and after infusions of graded doses of ACh, SNP or ANP in the absence or presence of 100 microM L-NMMA, and the levels of cyclic GMP were measured. Basal and ACh-induced cyclic GMP formations in the mesenteric arteries were significantly inhibited in the presence of L-NMMA, whereas a concomitant infusion of 300 microM L-arginine restored the inhibition of basal as well as ACh-induced cyclic GMP formations. L-NMMA did not affect SNP- and ANP-stimulated cyclic GMP formations, respectively. These results suggest that L-arginine is necessary for not only the stimulated cyclic GMP formation but also the basal cyclic GMP formation in the mesenteric arteries, whereas the SNP- and ANP-stimulated cyclic GMP formations in the arteries are independent of L-arginine.

Absorption spectral study of cytochrome P450d-phenyl isocyanide complexes: effects of mutations at the putative distal site on the conformational stability

Interactions of phenyl isocyanide (PheNC) with purified engineered cytochrome P450d wild type and putative distal mutants, Glu318Asp and Glu318Ala, were studied with optical absorption spectra. The wild type and the mutant Glu318Asp were purified as the high-spin state, while the mutant Glu318Ala was purified as the oxygen-bound low-spin form. Thus, it is suggested that Glu318 is important to make the appropriate heme environment of P450d. Spectral dissociation constants (0.19-0.39 mM) of the ligand for the ferric mutants were lower than that (0.74 mM) of the wild type. These dissociation constants were changed by adding a substrate, 7-ethoxycoumarin. The reduced wild type-PheNC complex showed a Soret peak at 451 nm, while the reduced mutant-PheNC complexes showed two peaks at 451 and 423 nm. The 451-nm peak of the complexes decreased with the concomitant increase of a new peak at 433 nm at room temperature. Thus, it was suggested that P450d can take two conformationally different forms from the characteristic spectral features. The Soret spectral conversions which followed the first-order kinetics were analyzed by changing the temperature. The activation energy (69 kcal/mol) for the conversion for the wild type was higher than those (37-50 kcal/mol) for the mutants. The activation energy for the wild type further increased (by 55%) by adding the substrate, while those for the mutants were essentially unchanged by adding the substrate. We discuss the important role of Glu318 at the putative distal site of P450d in the packing or the conformational stability of the putative distal site of the P450d molecule.

[Clinical study of tubular creatinine secretion in renal dysfunction]

Endogenous creatinine clearance (Ccr) has been much more commonly used to estimate renal function in clinical medicine, in comparison with inulin clearance (Cin) which is more accurate measure of glomerular filtration rate (GFR). There is, however, increasing difference between Ccr and Cin as renal function deteriorates. Since this difference is considered to be resulting from the tubular secretion of creatinine, Cin and Ccr were simultaneously measured in 81 patients with chronic renal disease, as well as 12 control subjects in this study. As Cin decreased, the Ccr/Cin ratio increased and the ratio varied widely even in patients with similar degree of renal impairment. The subjects were classified into 3 groups, group I (Cin greater than 80 ml/min), group II (80 ml/min greater than or equal to Cin greater than or equal to 40 ml/min) and group III (Cin less than 40 ml/min). The mean values of tubular creatinine secretion (Tcr) were 0.07 +/- 0.173 mg/min (+/- SD) in group I, 0.205 +/- 0.136 mg/min in group II and 0.333 +/- 0.139 mg/min in group III, respectively. Therefore, Tcr in the group of the severe impairment was the highest. In addition, Ccr and Cin were measured in 15 patients with chronic nephritis before and after an intravenous bolus injection of cimetidine (5 mg/kg BW). Following the injection Ccr/Cin ratio was reduced from an initial value of 1.51 +/- 0.23 to 1.18 +/- 0.13 in group II and from 2.00 +/- 0.44 to 1.55 +/- 0.25 in group III, respectively. Tubular secretion of creatinine appeared to be inhibited by cimetidine even in the patients with severe renal dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

[Studies on the dynamics of Salmonella organisms in raw sewage treatment plants]

The dynamics of Salmonella organisms in raw sewage treatment plants was studied over a period from July 1987 to August 1989. An experiment where Salmonella ser. Havana NAr was introduced into raw sewage was also performed over 2 days during this period. The results are as follows. 1) A number of strains of Salmonella could be isolated usually from samples drawn from raw sewage influent and up to the activated sludge stage of sewage processing. 2) After Salmonella ser. Havana NAr was introduced into raw sewage, the number of the organisms decreased in the activated sludge process to 1/1000 and the organisms were not found in the treatment plants after about forty days. 3) These results suggest that Salmonellas are adsorbed to activated sludge or other sludges, and are not discharged into rivers from this treatment plant. 4) The possibility of being able to determine the strain of Salmonella in regional epidemics by serovars of Salmonella detected in raw sewage treatment plants was suggested.

Effect of endothelin-3 (ET-3) on renal function in rat perfused kidney

We examined the effect of endothelin-3 (ET-3) at a high dose (pressor dose) and a low dose (non-pressor dose) in rat perfused kidney (PK), since ET-3 has recently been reported to exert a vasodilator action especially at a low dose. Kidneys were perfused with Krebs-Henseleit buffer at a fixed flow rate (6 ml/min) in situ. After collection of the renal venous effluent and urine for 20 min, vehicle (saline; n = 6), 10(-13)M ET-3 (low dose; n = 6) or 10(-8) M ET-3 (high dose; n = 6) was added to the perfusate, and sample collection was performed for the same period with each. The high dose of ET-3 significantly increased the perfusion pressure, fractional sodium excretion and synthesis of prostaglandins (PGs) consistently with a significant reduction in the glomerular filtration rate (GFR). On the other hand, the low dose of ET-3 significantly increased the GFR, urine volume and free-water clearance with no change in the perfusion pressure or synthesis of PGs. These findings suggest that a low dose of ET-3 can increase the glomerular capillary ultrafiltration coefficient and that ET-3 exerts an influence on sodium and water handing in the rat PK.

Deregulation of a homeobox gene, HOX11, by the t(10;14) in T cell leukemia

Molecular cloning of the t(10;14)(q24;q11) recurrent breakpoint of T cell acute lymphoblastic leukemia has demonstrated a transcript for the candidate gene TCL3. Characterization of this gene from chromosome segment 10q24 revealed it to be a new homeobox, HOX11. The HOX11 homeodomain is most similar to that of the murine gene Hlx and possesses a markedly glycine-rich variable region and an acidic carboxyl terminus. HOX11, while expressed in liver, was not detected in normal thymus or T cells. This lineage-restricted homeobox gene is deregulated upon translocation into the T cell receptor locus where it may act as an oncogene.

Cyclic GMP formation of resistance vessel in the development of hypertension in spontaneously hypertensive rats

We investigated the basal levels and responses of cyclic GMP (cGMP) derived from perfused mesenteric arteries to acetylcholine (ACh) and sodium nitroprusside (SNP) in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) at different ages, in order to evaluate the basal and stimulated release of endothelium-derived relaxing factor (EDRF) from the resistance vessel during the development of hypertension. The mesenteric arteries were removed from 8-, 12- and 20-week-old WKY and SHR, and were perfused with Krebs-Henseleit solution containing 0.2 mM isobutyl methyl xanthine. The effluents from the perfused arteries were corrected before and after infusions of graded doses of ACh or SNP, and the levels of cGMP were measured. The basal levels of cGMP from the mesenteric arteries in the 12- and 20-week-old SHR were significantly lower than those in age-matched WKY. A negative correlation was observed between the basal levels of cGMP and the systolic blood pressure in SHR, but not in WKY, among all ages. On the other hand, there were no differences in the responses of cGMP to infusion of ACh between the WKY and SHR at each age. Moreover, the responsiveness of cGMP to infusion of SNP in the 12-week-old SHR was much higher than that in age-matched WKY. These data suggest that the basal cGMP formation in the arteries which may reflect the basal release of EDRF is reduced in older SHR and is associated with the development of hypertension, and that the stimulated release of EDRF is not associated with the development of hypertension.

Tubuloglomerular feedback resetting in different models of acute volume expansion

Our results revealed that renal blood flow (RBF) increased during both isooncotic and hypooncotic plasma expansion by 4% of body weight (BW). Tubuloglomerular feedback (TGF) sensitivity assessed by the measurement of proximal stop-flow pressure at loop perfusion rates of 0 to 40 nl/min and RBF autoregulation were not substantially affected by this degree of volume expansion, provided plasma oncotic pressure did not change. This upward shift of the TGF response curve together with maintenance of an RBF autoregulation during plasma expansion lead to the conclusion that the TGF mechanism apparently plays a significant role in the control of glomerular hemodynamics, despite the marked vasodilation occurring during acute volume expansion.

Low doses of endothelin-3 elicit endothelium dependent vasodilation which accompanies with elevation of cyclic GMP

Low doses (10(-16)-10(-10) M) of endothelin-3 (ET-3) elicited continuous vasodilations of mesenteric arteries preconstricted with norepinephrine (NE) but not with KCl. In arteries perfused with Ca2+ free solution, ET-3 did not affect the perfusion pressure. In endothelium-denuded arteries preconstricted with NE, ET-3 significantly elevated the perfusion pressure in a dose-related manner. The levels of cyclic GMP and cyclic AMP from the intact arteries were significantly elevated by ET-3; the cyclic GMP elevasion disappeared with methylene blue. Following endothelium-denudation, cyclic GMP elevation was abolished, but cyclic AMP elevation was unaffected. Levels of 6-Keto-PGF1 alpha in the arteries were not changed appreciably by ET-3. These data indicate that the vasodilating effects of ET-3 depend on the presence of extracellular Ca2+ and the existence of endothelium. They are accompanied by elevations of cyclic nucleotides and the elevation of cyclic GMP depends on the endothelium. It is possible that the vasodilating effects of low doses of ET-3 are associated with endothelium-derived relaxing factor.

[Acute congestive heart failure due to malignant rheumatoid arthritis]

A 54-year-old woman with malignant rheumatoid arthritis was admitted with acute congestive heart failure and pulmonary hypertension. The precipitating antibody to nuclear ribonucleoprotein (nRNP) was highly positive. Her hands and feet showed typical rheumatoid deformities and Raynaud's phenomenon. In a few days her feet became to necrosis due to vasculitis. "Pulse" methylprednisolone and prednisone therapy resulted in normalization of seropositivity, and left ventricular ejection fraction with symptoms of congestive heart failure, and the elimination of ECG abnormalities. Recognition of symptoms of left ventricular dysfunction in patients with rheumatoid arthritis should prompt testing for active arteritis and/or myocarditis, because dramatic improvement may result from immunosuppressive therapy.

CO binding studies of engineered cytochrome P-450ds: effects of mutations at putative distal sites in the presence of polycyclic hydrocarbons

The kinetic parameters of CO binding to genetically engineered cytochrome P-450d (P-450d) and two putative distal mutants, Glu318Asp and Thr322Ala, have been evaluated in the presence and absence of polycyclic hydrocarbons. The dissociation constant (Kd) of CO from wild-type P-450d was decreased by half (from 1.8 microM to approximately 0.9 microM) in the presence of phenanthrene or anthracene but was increased to 11 microM in the presence of 1,2:3,4-dibenzanthracene or 7,8-benzoflavone. These changed Kd values were not altered markedly by mutations at the putative distal site. In contrast, the recombination rate constants (kon) of CO to the Glu318Asp mutant in the presence of phenanthrene (15.5 X 10(5) M-1 s-1) and 7,8-benzoflavone (0.75 X 10(5) M-1 s-1) were much larger than those for the wild type. Similar but smaller increases of the kon values were observed for the Thr322Ala mutant. It was suggested that phenanthrene and anthracene distort the Fe-C-O bond and/or affect the access of CO to wild-type P-450d in an opposite way from 1,2:3,4-dibenzanthracene and 7,8-benzoflavone. Glu318 and Thr322 may be located so close to a CO binding channel in ferrous P-450d that mutations of these residues can open the sterically hindered CO channel caused by the hydrocarbons.

A case of primary systemic amyloidosis with AA protein

We present here a case of young adult-onset primary systemic amyloidosis with AA protein. A 29-year-old male presenting with macrohematuria was transferred to our hospital because of aggravation of renal function. Amyloid protein was detected in the bladder, stomach and thyroid. The amyloid protein proved to be AA type by potassium permanganate histochemical analysis. Since secondary amyloidosis was excluded by the laboratory data and there was no family history of amyloidosis, a diagnosis of primary systemic amyloidosis with AA protein was reached. Although the patient was prescribed dimethyl sulphoxide, his renal function worsened with gastrocolic symptoms and a bleeding tendency. Hemodialysis (HD) was then initiated. After starting the HD, the patient's general condition recovered and subsequently the patient on treatment with maintenance HD was discharged.

Pharmacokinetics and optimum dose of disopyramide in patients with chronic renal failure

The pharmacokinetics and optimum dose for maintenance of disopyramide (DP) which is effective against arrhythmia were studied in patients with chronic renal failure (CRF, n = 10), who had a creatinine clearance (Ccr) less than 30 ml/min. The plasma concentrations (PC) of DP and mono-isopropyl-disopyramide (MDP) an active metabolite of DP, were measured by high performance liquid chromatography. Samples from patients and controls were obtained at 0, 1, 2, 3, 4, 6, 8, 12, 24, 33, and 48 hr after oral administration (OA) of 100 mg DP. The pharmacokinetic parameters were calculated using a two-compartment model. In CRF, the plasma half life (T 1/2) of DP was 5.25 to 22.42 hr (average is 12.45 hr) and that of MDP was 5.09 to 131.66 hr (average is 16.9 hr). In normal controls, the T 1/2 of DP was 6.05 hr, but that of MDP could not be determined the available sensitivity of measurement. T max was 3.11 hr at the total PC of DP and MDP, and C max was 2.48 g/ml on average. In conclusion, the present study revealed that: (1) the PC of a mixture of DP and MDP should rise following OA of DP every 8 or 12 hr in CRF; (2) it is necessary therefore to monitor the accumulation of MDP after rolling OA of DP; and (3) OA of DP every 24 hr can maintain an effective PC.

An approach to optimal dialysis using urea kinetic modeling

Urea kinetic modeling (UKM) was carried out to evaluate the water control in patients undergoing long-term hemodialysis. In 21 patients on chronic dialysis, the results of two different determinations of the total body water, i.e. by the deuterium oxide (D2O) method and by UKM, were compared. A correlation was observed with Y = 0.98X + 5.9 (P less than 0.01, r = 0.91) for males and Y = 0.97X + 6.2 (P less than 0.01, r = 0.90) for females, indicating that UKM is useful for determining the total body water. In addition, the 21 patients were classified into two groups based on their ECG findings, and UKM was performed in the two groups for comparison. The values of the total body water were 68.5 +/- 4.0% and 68.6 +/- 6.2% of body weight, respectively, with no significant difference between them. However, the CTR was 50.2 +/- 2.8% and 46.2 +/- 4.4%, respectively. Thus, not only X-ray examinations but also UKM should be carried out to determine the standard weight (SW-DW) in the presence of cardiac dysfunction. Instructions for water control were given when the total body water exceeded 73% during the UKM measurements over 5 years, which allowed an optimal total body water to be maintained thereafter. The possible influence of erythropoietin (EPO) was also examined by performing UKM in 8 cases receiving EPO and 7 cases without EPO. No noticeable difference was observed between the two groups. 17 patients using a polyacrylonitrile (PAN) membrane were further divided into those with and those without EPO to evaluate the possible influence of the PAN membrane-EPO combination. As a result, no significant difference was demonstrated, suggesting that UKM can be satisfactorily performed under such conditions. In 11 patients on chronic dialysis, the levels of alpha-human atrial natriuretic peptide (alpha-hANP) were measured pre- and post-dialysis to examine the relationship between the change in alpha-hANP and rate of weight loss (%). A significant correlation was observed with Y = 12.8X + 5.1 (P less than 0.05, r = 0.68). In conclusion, UKM was found to be useful for evaluating the water control and for assessing the optimal dialysis in patients receiving long-term hemodialysis.

IgG response is impaired in H2-c-fos transgenic mice

Transgenic mice carrying the proto-oncogene c-fos under the control of H-2Kb promoter (c-fos mice) were generated from (C57BL/6 x SJL)F2 mice. One line was backcrossed with C57BL/6 mice for 10 generations. These semi-congenic c-fos mice express exogenous c-fos RNA in their hematopoietic tissues. The following immunological states are apparent. (i) Titers of serum IgM, IgG, and IgA of naive c-fos were within the control range. (ii) These mice could not produce primary IgG antibody specific for immunized antigen. (iii) Production of primary IgM and IgA antibody to the antigen was within the control range. (iv) There were no IgG memory B cells generated in the spleens of c-fos mice. (v) Activities of antigen-presenting cells and carrier-specific helper T cells from c-fos mice were normal. These findings strongly suggest that the immune abnormality of c-fos mice is in limiting B cell function to the production of IgG to immunized antigens.

Effects of indomethacin, endothelium-denudation, methylene blue and L-NG-monomethyl arginine on the vasoactive effects of endothelin-3

To clarify the mechanisms underlying the vasoactive effects of endothelin-3 (ET-3), we examined the effects of indomethacin, endothelium-denudation, methylene blue and L-NG-monomethyl arginine (L-NMMA) on the perfusion pressures of isolated rat mesenteric arteries infused with ET-3. ET-3 at 10(-15)-10(-8) M elicited significant vasodilations in a dose-related manner, in which 10(-9) and 10(-8) M ET-3 caused biphasic pressure changes involving a transient dilation and subsequent vasoconstriction. Five micromolar indomethacin did not affect the vasodilations and vasoconstrictions induced by ET-3. In endothelium-denuded arteries, 10(-13)-10(-8) M ET-3 elicited significant vasoconstriction in a dose-related manner without any vasodilation. In the presence of 30 microM methylene blue, the vasodilations induced by ET-3 disappeared. In the presence of 100 microM L-NMMA, 10(-15)-10(-8) M ET-3 elicited significant vasoconstrictions in a dose-related manner, and the vasodilation by ET-3 existed only at 10(-8) M ET-3. These data suggest that the vasodilating effects of low doses of ET-3 through the endothelium overcome the vasoconstricting effects, and that the vasodilating effects of ET-3 are associated with an endothelium-derived relaxing factor as an endothelium-derived nitric oxide.