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M Suematsu

Publications and source records attributed to M Suematsu.

At least 109 records · Page 6Linked to original sources
PubMed1994

Augmented receptor-mediated Ca2+ mobilization causes supersensitivity of contractile response to serotonin in atherosclerotic arteries.

We have previously reported that atherosclerotic arteries obtained from Watanabe heritable hyperlipidemic (WHHL) rabbits exhibit a marked increase of contractile response to serotonin (5-hydroxytryptamine [5-HT]) and ergonovine and that these augmented contractile responses to specific agonists may play an important role in the pathogenesis of vasospasm. In the present study, we investigated whether supersensitivity to 5-HT in atherlosclerotic arteries was due to an increase in 5-HT receptor-mediated Ca2+ mobilization or to an increase in Ca2+ sensitivity of the contractile elements. We measured simultaneously both isometric tension and [Ca2+]i in fura 2-loaded aortic smooth muscle strips from control and WHHL rabbits. Muscle tension in the high K+ (72.7 mmol/L)-stimulated states and [Ca2+]i in both resting and high K(+)-stimulated states did not differ between control and WHHL rabbits. In atherosclerotic aortas from WHHL rabbits, the dose-response curves of both tension and [Ca2+]i for 5-HT were shifted to the left at lower threshold concentrations and one-half maximally effective dose. The maximum response of contraction produced by 5-HT in WHHL rabbits was augmented compared with that in control rabbits (123 +/- 17% versus 33 +/- 7% of the 72.7 mmol/L K(+)-induced contraction, P < .001). The maximum response of [Ca2+]i produced by 5-HT was also augmented in WHHL rabbits compared with control rabbits (29 +/- 4% versus 10 +/- 0.9% of the 72.7 mmol/L K(+)-induced [Ca2+]i, P < .001). In contrast, the responses of contraction and [Ca2+]i to phenylephrine were similar between control and WHHL rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Prostaglandin E1 abrogates early reductive stress and zone-specific paradoxical oxidative injury in hypoperfused rat liver.

This study was designed to investigate the effects of prostaglandin E1 on reductive stress and the subsequent oxidative cell injury in hypoperfused rat liver. The intralobular heterogeneity of hepatocellular redox state, mitochondrial dysfunction, and intracellular hydroperoxide formation were visually monitored by digital microfluorography of pyridine nucleotide autofluorescence, rhodamine 123, and dichlorofluorescein fluorescence, respectively. Under the 25% low flow perfusion, pyridine nucleotide autofluorescence increased time-dependently and reached a steady state at 10 min among the entire lobules. The decrease in mitochondrial membrane potential was > 20 mV in all portions of the lobules at 60 min. The onset of hydroperoxide formation was observed at 40 min in the marginally oxygenated proximal portion of anoxic pericentral regions and the oxidative impact reached a maximum level at 60 min. Sodium (-)-8-(3-methoxy-4-phenylsulfinylphenyl) pyrazo [1,5-a]-1,3,5-triazine-4-olate monohydrate (BOF 4272), a novel xanthine oxidase inhibitor, suppressed the zone-specific oxidative changes without attenuating the increase in pyridine nucleotide autofluorescence and mitochondrial dysfunction. Pretreatment with prostaglandin E1 not only abrogated an early increase in pyridine nucleotide fluorescence and mitochondrial dysfunction induced by hypoperfusion but also diminished the subsequent midzonal oxidative injury. Since prostaglandin E1 has no oxyradical-scavenging action, the preventive effect of this reagent on the hypoxia-induced oxidative cell injury is attributable to the attenuation of mitochondrial dysfunction. These results suggest that, in low flow hypoxia, early reductive stress plays a key role in the initiation of xanthine oxidase-mediated midzonal oxidative changes, which may lead to subsequent centrilobular necrosis.

Alprostadil↗
PubMed1994

Spatial and temporal correlation between leukocyte behavior and cell injury in postischemic rat skeletal muscle microcirculation.

BACKGROUND: Although leukocyte adhesion and capillary plugging are postulated to play a role in postischemic tissue injury, there is only limited evidence demonstrating the relationship between tissue leukocyte accumulation and cell injury in terms of their temporal sequence and spatial distribution. EXPERIMENTAL DESIGN: This study was designed to study in vivo neutrophil behavior and its correlation with cell injury in postischemic skeletal muscle microcirculation. The microcirculation of the rat spinotrapezius muscle was observed in vivo using dual-color digital microfluorography to simultaneously visualize leukocyte traffic and cell death (irreversible nuclear damage) on the basis of carboxyfluorescein diacetate succinimidyl ester and propidium iodide, respectively. A 1-hour period of hemorrhagic hypotension (40 mm Hg) followed by reperfusion was carried out to induce muscle injury. RESULTS: Hypotension was followed by an increase in leukocyte recruitment in two different ways: capillary obstruction and venular adhesion. Upon reperfusion, a majority of the leukocytes were initially dispersed from the muscle capillaries and venules, but then the number of leukocytes plugging capillaries and adherent to venules increased again in a time-dependent manner. The number of leukocytes obstructing capillaries was closely correlated with the postischemic systemic blood pressure. The cell injury became detectable initially at the end of the hypotensive period and then increased explosively after reperfusion before a significant leukocyte accumulation. Reperfusion-induced early nuclear injury was seen predominantly in reperfused capillaries without plugging leukocytes. A majority of the initially damaged nuclei were those of myocytes in the pericapillary space, but no nuclei of capillary endothelium was involved. Sodium (-)-8-(3-methoxy-4-phenylsulfinylphenyl) pyrazolo [1,5-a]-1,3,5-triazine-4-olate monohydrate, a novel inhibitor of xanthine oxidase, significantly attenuated the early increase in muscle injury and subsequent venular leukocyte adhesion after reperfusion. CONCLUSIONS: These results suggest the involvement of an endothelium-dependent mechanism involving xanthine oxidase in postischemic irreversible myocyte injury. It is conceivable that leukocytes adherent to venules as well as those plugging capillaries play only minor roles in the initial mechanism of reperfusion injury.

Animals↗
PubMed1993

Effect of prolonged administration of clonidine on [3H]PN 200-110 and [125I]omega-conotoxin binding in mouse brain.

The effect of chronic exposure to clonidine or morphine on clonidine- and morphine-induced analgesia in mice was examined. Binding of L- or N-type calcium channel antagonist to cortical membrane fractions was also compared between these groups of mice. A decrease in the analgesic effect of clonidine and morphine was observed following prolonged administration of clonidine or morphine. Binding of [3H]PN 200-110, an L-type calcium channel antagonist, decreased following prolonged administration of clonidine whereas it increased after morphine treatment. On the other hand, a significant increase of [125I]omega-conotoxin, an N-type calcium channel antagonist, binding was observed after chronic clonidine or morphine treatment. These results will be discussed in relation with the possible development of cross-tolerance between clonidine and morphine through the change in calcium channels, more specifically in N-type channels.

Animals↗
PubMed1993

Activation of nitric oxide synthase from cultured aortic endothelial cells by phospholipids.

Nitric oxide is a recently discovered biomolecule with a broad range of actions and synthesized by nitric oxide synthases. We investigated effects of lipids on particulate nitric oxide synthase purified from cultured bovine aortic endothelial cells by monitoring the conversion of L-[3H]arginine to L-[3H]citrulline. Phosphatidylcholine, lysophosphatidylcholine, and phosphatidylethanolamine dose-dependently enhanced the enzyme activity up to 3 fold in the presence of Ca2+, calmodulin, NADPH, FAD, and (6R)-5,6,7,8-tetrahydrobiopterin. These phospholipids increased the Vmax of nitric oxide synthase without altering the Km for L-arginine and the affinities for Ca2+ and calmodulin. These findings suggest that phospholipids play an important role in modulating endothelial nitric oxide synthase activity.

Amino Acid Oxidoreductases↗
PubMed1993

Nitric oxide mediates Kupffer cell-induced reduction of mitochondrial energization in hepatoma cells: a comparison with oxidative burst.

The metabolic changes in rat hepatoma cell line, AH70 cells, after coculturing with Kupffer cells were visualized using a silicon-intensified target camera and subsequent processing with a computer-assisted digital imaging processor. In cocultured tumor cells, nonactivated Kupffer cells reduced mitochondrial energization as indicated by the decrease in the fluorescence intensity of rhodamine 123 (Rh123) and induced lipid peroxidation as shown by the dichlorofluorescein (DCF) activation. The reduction in Rh123 could be eliminated by addition of an analogue of L-arginine (NG-monomethyl-L-arginine), suggesting the involvement of nitric oxide (NO.) in the decrease in mitochondrial energization. Superoxide dismutase did not inhibit the reduction in Rh123 but significantly inhibited DCF activation. These findings indicate that the latter reaction was mediated by superoxide anion. Two h after the cells were cocultured, propidium iodide-positive, severely injured tumor cells significantly increased in number. This increase was significantly attenuated by addition of NG-monomethyl-L-arginine but not by superoxide dismutase, suggesting that NO. may be greatly involved in Kupffer cell-mediated injury of AH70 cells. In another set of experiments, the culture medium of Kupffer cells caused no significant alteration of Rh123, DCF, and propidium iodide-associated fluorescences in AH70 cells. In addition, ultrastructural observation revealed that the membrane-to-membrane attachment between Kupffer cells and tumor cells occurred within 30 min after coculturing. These results suggest that Kupffer cell-derived NO. release, triggered by the close contact with tumor cells, may induce damage to tumor cells via inhibition of mitochondrial energization.

Animals↗
PubMed1993

Characterization of rat LECAM-1 (L-selectin) by the use of monoclonal antibodies and evidence for the presence of soluble LECAM-1 in rat sera.

We have characterized the rat LECAM-1 (L-selectin) by the use of newly generated hamster anti-rat LECAM-1 monoclonal antibodies (mAb) (HRL1, HRL2, HRL3, HRL4), with respect to the biochemistry, cellular distribution and function, and developed an ELISA system to detect the soluble form of rat LECAM-1. In the rat, lymphocyte and neutrophil LECAM-1 have apparent molecular masses of 65 and 62 kDa, respectively, and differential glycosylation may account for the molecular heterogeneity. Readily detectable levels of LECAM-1 are expressed on peripheral blood lymphocytes and neutrophils, but not on thymocytes. Lymphocyte LECAM-1 is rapidly shed from the cell surface upon cell activation with PMA, but not with interleukin (IL)-8. In contrast, neutrophil LECAM-1 showed rapid shedding upon stimulation with phorbol 12-myristate 13-acetate (PMA) or IL-8. Concomitantly there is up-regulated expression of Mac-1 in PMA- and IL-8-stimulated neutrophils. Neutrophil rolling in mesenteric venules was significantly inhibited by administration of function-blocking anti-rat LECAM-1 mAb HRL3, but not by non-blocking HRL4, indicating that LECAM-1 plays a significant role in leukocyte rolling. Given that LECAM-1 is rapidly shed from the cell surface, we attempted to develop an ELISA system for detecting LECAM-1 is soluble form, and measured the levels in experimental autoimmune uveitis. The circulating levels of LECAM-1 increased from day 4, which preceded the appearance of clinical signs of uveitis and remained high until uveitis subsided, suggesting that soluble LECAM-1 is potentially a useful parameter to monitor certain types of inflammatory or immune disorders.

Acute-Phase Reaction↗
PubMed1993

Intravital and electron microscopic observation of Ito cells in rat hepatic microcirculation.

Intralobular distribution of Ito cells (fat-storing cells) in hepatic microcirculatory units was investigated through intravital fluorescence microscopy. By using a low-level ultraviolet epi-illumination and a sensitive silicon intensified target camera, the intrahepatic autofluorescence was visualized and digitally processed. In rats fed an ordinary diet, the ultraviolet-excited autofluorescence was composed of at least two different origins that could not be spectrophotometrically distinguished, namely, multiple patchy autofluorescence activities along the sinusoids and terminal hepatic venules and diffuse parenchymal autofluorescence. Multiple patchy activities showed a rapid photobleaching phenomenon under the continuous ultraviolet excitation. These fluorescent activities were completely eliminated by depleting the intrahepatic retinoid contents using a vitamin A-deficient diet for 4 weeks. Furthermore repeated administration of vitamin A significantly enhanced the patchy fluorescent activities. Electron microscopy revealed that these vitamin A fluorescent activities are colocalized with the fat droplets in Ito cells, providing evidence that Ito cells exist not only in perisinusoidal spaces but also in the perivascular spaces of the terminal hepatic and portal venules. The current intravital technique thus provides a new method to observe Ito cells in hepatic microcirculatory units in vivo.

Animals↗
PubMed1993

Oxyradical generation from leukocytes during endotoxin-induced microcirculatory disturbance in rat mesentery--attenuating effect of cetraxate.

By using the intravital microscope equipped with digital imaging processor, we investigated the granulocyte-mediated oxidative burst during the endotoxin-induced microvascular derangement in rat mesentery. The leukocyte behavior after the injection of acridine orange was detected by using a silicon-intensified target camera, the erythrocyte velocity was measured by using a high-speed video camera system, and the luminol-dependent photoemission was visualized by an ultrasensitive photon-counting camera in lipopolysaccharide (LPS)-treated microvascular beds. At 60 min after the LPS administration, a significant leakage of FITC-labeled albumin was observed along mesenteric venules under a fluorescence microscopy. The number of sticking leukocytes increased in association with the decrease in erythrocyte velocity after starting the LPS infusion. The luminol-dependent chemiluminescence in microvascular beds gradually increased over that recorded prior to LPS exposure and was fourfold higher 60 min after the start of LPS infusion. The distribution of the photoemission clearly corresponded to the venular endothelium, to which leukocytes adhered. In blood samples taken from the mesenteric vein at 60 min after the LPS administration, a decrease in the number of granulocytes and increases of total and individual chemiluminescence activities were observed. These results suggest that LPS induces oxidative burst from granulocytes on the venular endothelium. Cetraxate, an inhibitor of proteases including plasmin, significantly inhibited the leukocyte activation and prevented alterations in microvascular hemodynamics induced by LPS in vivo, whereas it had no effect on the LPS-induced oxyradical generation from adherent leukocytes in vitro. The present study demonstrates that proteases such as plasmin may play an important role in the pathogenesis of endotoxin-induced microvascular disturbances.

Animals↗
PubMed1993

Xanthine oxidase-mediated intracellular oxidative stress in response to cerulein in rat pancreatic acinar cells.

Intralobular oxygen radical formation was examined in cerulein-stimulated rat pancreatic acinar cells by digital imaging microscopic fluorography using a hydroperoxide-sensitive fluorescent probe, dichlorofluorescin (DCFH) diacetate. The isolated pancreatic acinar cells loaded with DCFH diacetate were microscopically observed, and the dichlorofluorescein (DCF) fluorescence yielded by DCFH oxidation via hydroperoxides was digitally processed. Within the initial 20 min after the application of cerulein (10 microM), intracellular oxidative stress was observed as indicated by the increase in DCF fluorescence intensity and reached its maximum at 60 min. DCF fluorescence intensity was then gradually decreased until 80 min, followed by a marked increase in propidium iodide (PI) fluorescence, suggesting irreversible cell death. Allopurinol (1 microM), a xanthine oxidase inhibitor, significantly attenuated the early increase of DCF fluorescence intensity as well as the late cell damage. Treatment with hyperbaric oxygen (PO2 300 mm Hg) also significantly attenuated both the increase of DCF fluorescence and the number of PI-positive cells. The results suggest that xanthine oxidase-mediated oxygen radicals may play an important role in cerulein-induced intracellular oxidative stress in pancreatic acinar cells of rats.

Animals↗
PubMed1993

Attenuation of endotoxin-induced intestinal microcirculatory damage by eicosapentanoic acid.

The major objective of this study is to investigate whether oral administration of eicosapentanoic acid (EPA) has any preventive effect on endotoxin-induced microcirculatory damage of rat small intestine. EPA in a daily dose of 300 mg/kg was orally given to male Wistar rats for 3 wk. Submucosal microvessels of the ileum were observed by intravital microscopy equipped with a high-speed video camera system after the intra-arterial infusion of endotoxin at a dose of 2 mg.kg-1.h-1. The number of sticking leukocytes was significantly increased at 30 min after the treatment of endotoxin especially along the smaller branch of intestinal venules. It reached the maximal plateau at 45 min after treatment. The pretreatment of EPA significantly attenuated the increase in sticking leukocytes induced by endotoxin. A platelet-activating factor (PAF) antagonist 2-[N-acetyl-N-(2-methoxy-3-octadecylcarbamoyloxy propoxycarbonyl) aminomethyl]-1-ethylpyridinium chloride (CV-6209) significantly prevented the increased leukocyte sticking to the same extent as EPA treatment. Thirty minutes after endotoxin infusion, red blood cell (RBC) velocity was significantly decreased in both arterioles and venules. RBC velocity appeared to be continuously decreased thereafter and reached its minimum value at approximately 60 min. EPA treatment was revealed to prevent the decrease in RBC velocity of microvessels induced by endotoxin. CV-6209 also significantly attenuated the decreased RBC velocity. The remarkable elevation of PAF content in the ileal mucosa as observed by endotoxin infusion was also significantly attenuated by administration of EPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

In vivo visualization of oxidative changes in microvessels during neutrophil activation.

This study was designed to characterize temporal changes of oxidative metabolism in microvascular endothelium in vivo associated with neutrophil adhesion and diapedesis. The rat mesentery was loaded with dichlorofluorescein (DCFH) diacetate, a hydroperoxide-sensitive fluorescent probe that is trapped within viable cells as a nonfluorescent form and is converted to fluorescent dichlorofluorescein (DCF) by hydroperoxides. The fluorescent light emission was recorded with digital microscopy and its camera response was calibrated by superfusion of the mesentery with known concentrations of hydroperoxides. After rinsing with a precursor-free solution, it was possible to observe both the neutrophil adhesion and fluorescence changes in venular endothelium during superfusion with platelet-activating factor (PAF, 100 nM) by alternately changing light sources. In the PAF-treated animals, DCF fluorescence in the venular wall was markedly elevated concurrent with an increase in the number of adherent neutrophils. An onset of a significant DCF fluorescence was observed as early as 10 min after PAF application. The venular oxidative changes were co-localized with neutrophils adhering to the endothelium or migrating into the interstitium. The oxidative impact in the venular wall superfused with 100 nM PAF for 40 min was equivalent to that induced by the 10-min superfusion of 0.8 mM of tert-butyl hydroperoxide. Pretreatment with dipyridyl, an iron chelator, or dimethylthiourea, a hydroxyl radical scavenger, significantly attenuated the PAF-induced oxidative changes in the venule but had little effect on neutrophil adhesion. These findings suggest that an endothelial cell-dependent mechanism involving an iron-catalyzed reaction may have a role in enhancement of neutrophil-mediated oxidative stress in venular endothelium.

2,2'-Dipyridyl↗
PubMed1993

High density lipoprotein reverses inhibitory effect of oxidized low density lipoprotein on endothelium-dependent arterial relaxation.

We have recently reported that oxidized low density lipoprotein (ox-LDL) inhibits endothelium-dependent arterial relaxation through its increased lysophosphatidylcholine (LPC). In this study we examined whether high density lipoprotein (HDL) has any effect on the inhibition of endothelium-dependent relaxation by ox-LDL in isolated strips of rabbit thoracic aorta. Both low density lipoprotein (LDL) and HDL were isolated from normal human plasma, and LDL was oxidized by exposure to copper. Preincubation of arterial strips with ox-LDL (0.1-0.5 mg protein/ml) inhibited endothelium-dependent relaxation to acetylcholine (ACh) in a concentration-dependent manner. HDL (1 mg protein/ml) by itself had no effect on the relaxation to ACh. In the presence of HDL, the inhibition by ox-LDL was markedly reduced. Although synthetic L-alpha-palmitoyl LPC (5 micrograms/ml) completely abolished a relaxation to ACh, the preincubation of arterial strips with HDL completely prevented the LPC-induced inhibition. Moreover, a relaxation to ACh was almost completely recovered when the strips were washed with buffer containing HDL even after LPC-induced inhibition had occurred. HDL markedly reduced the incorporation of [1-14C]palmitate-labeled LPC ([14C]LPC) into cultured bovine aortic endothelial cells and promoted the release of cell-incorporated [14C]LPC into the medium, resulting in a reduction of the remaining [14C]LPC in the cells. Agarose electrophoresis after incubation of a mixture of ox-LDL labeled with [14C]LPC and unlabeled HDL demonstrated a transfer of [14C]LPC from ox-LDL to HDL. These results indicate that HDL reverses the ox-LDL-induced impairment of endothelium-dependent relaxation by removing LPC from ox-LDL and preventing LPC from acting on the endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1993

Nitric oxide mediates vasoactive effects of endothelin-3 on rat mesenteric microvascular beds in vivo.

In order to clarify whether the vasoactive effects of endothelin-3 (ET-3) on microvessels are associated with the endothelium-derived relaxing factor (EDRF) in vivo, the authors examined the effects of L-NG-monomethyl arginine (L-NMMA), an analog of L-arginine, on low-dose ET-3 induced hemodynamic changes in the mesenteric microcirculation of male Wistar rats. The intravital observation revealed that ET-3 100 pM induced a remarkable and periodic vasoconstriction in arterioles, and the constriction was sustained for approximately fifteen minutes. No remarkable change was observed in the microvessels after the superfusion of 1 pM ET-3. Superfusion of 1 pM ET-3 with 100 microM L-NMMA elicited the vasoconstriction in arterioles, and the arteriolar diameter recovered to the control level within ten minutes in spite of continuing the superfusion. The vasoconstriction induced by low-dose ET-3 with L-NMMA was suppressed by the additional superfusion of 200 microM L-arginine. The present study suggests that the recovery of arteriolar diameter after the ET-3-induced constriction may be mediated by nitric oxide at least in the early phase.

Animals↗
PubMed1993

Nitric oxide mediates lipopolysaccharide-induced alteration of mitochondrial function in cultured hepatocytes and isolated perfused liver.

The influence of endogenous nitric oxide, which is generated by stimulation with lipopolysaccharide, on the mitochondrial energization of rat hepatocytes was investigated in vitro and ex vivo. Using a fluorescence microscope equipped with a silicon intensifier target camera, we visualized fluorescence of rhodamine-123, a mitochondrial energization-sensitive fluorescence probe, in individual hepatocytes and measured the fluorescence intensity with a digital imaging processor. Although addition of Kupffer cells or lipopolysaccharide in a range of 0.1 to 1.0 microgram/ml caused no significant alteration in the fluorescence in hepatocytes, Kupffer cells plus 1.0 microgram/ml lipopolysaccharide reduced fluorescence intensity in the cocultured hepatocytes. The alteration of rhodamine-123 fluorescence in the hepatocytes induced by lipopolysaccharide-activated Kupffer cells was significantly inhibited by the addition of NG-monomethyl-L-arginine, a selective inhibitor of nitric oxide synthesis. The transportal infusion of lipopolysaccharide also decreased rhodamine-123 fluorescence in perfused rat liver. The decrease was significantly enhanced in the pericentral regions. Autofluorescence of NADH was elicited by continuous infusion of lipopolysaccharide; this reaction was also enhanced in the pericentral regions. We showed the main site of uptake of infused lipopolysaccharide in the hepatic lobule to be in the periportal regions with fluorescein isothiocyanate-labeled lipopolysaccharide. Our results indicate that the inhibition of mitochondrial energization occurs mainly in pericentral regions, which are distant from the lipopolysaccharide uptake site. The continuous administration of NG-monomethyl-L-arginine significantly attenuated the lipopolysaccharide-induced decrease in rhodamine-123 fluorescence and increase of the NADH contents of the hepatic lobule.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗