Biomedical subjects

Hidezo Mori

Publications and source records attributed to Hidezo Mori.

At least 55 records · Page 3Linked to original sources

PubMed2004

In situ measurements of crossbridge dynamics and lattice spacing in rat hearts by x-ray diffraction: sensitivity to regional ischemia.

BACKGROUND: Synchrotron radiation has been used to analyze crossbridge dynamics in isolated papillary muscle and excised perfused hearts with the use of x-ray diffraction techniques. We showed that these techniques can detect regional changes in rat left ventricle contractility and myosin lattice spacing in in situ ejecting hearts in real time. Furthermore, we examined the sensitivity of these indexes to regional ischemia. METHODS AND RESULTS: The left ventricular free wall of spontaneously beating rat hearts (heart rate, 290 to 404 bpm) was directly exposed to brief high-flux, low-emittance x-ray beams provided at SPring-8. Myosin mass transfer to actin filaments was determined as the decrease in reflection intensity ratio (intensity of 1,0 plane over the 1,1 plane) between end-diastole and end-systole. The distance between 1,0 reflections was converted to a lattice spacing between myosin filaments. We found that mass transfer (mean, 1.71+/-0.09 SEM, n=13 hearts) preceded significant increases in lattice spacing (2 to 5 nm) during systole in nonischemic pericardium. Left coronary occlusion eliminated increases in lattice spacing and severely reduced mass transfer (P<0.01) in the ischemic region. CONCLUSIONS: Our results suggest that x-ray diffraction techniques permit real-time in situ analysis of regional crossbridge dynamics at molecular and fiber levels that might also facilitate investigations of ventricular output regulation by the Frank-Starling mechanism.

Actin Cytoskeleton↗

PubMed2004

Beta-adrenoceptor blocker carvedilol provides cardioprotection via an adenosine-dependent mechanism in ischemic canine hearts.

BACKGROUND: Carvedilol is a beta-adrenoceptor blocker with a vasodilatory action that is more effective for the treatment of congestive heart failure than other beta-blockers. Recently, carvedilol has been reported to reduce oxidative stress, which may consequently reduce the deactivation of adenosine-producing enzymes and increase cardiac adenosine levels. Therefore, carvedilol may also have a protective effect on ischemia and reperfusion injury, because adenosine mediates cardioprotection in ischemic hearts. METHODS AND RESULTS: In anesthetized dogs, the left anterior descending coronary artery was occluded for 90 minutes, followed by reperfusion for 6 hours. Carvedilol reduced the infarct size (15.0+/-2.8% versus 40.9+/-4.2% in controls), and this effect was completely reversed by the nonselective adenosine receptor antagonist 8-sulfophenyltheophylline (45.2+/-5.4%) or by an inhibitor of ecto-5'-nucleotidase (44.4+/-3.6%). There were no differences of either area at risk or collateral flow among the various groups. When the coronary perfusion pressure was reduced in other dogs so that coronary blood flow was decreased to 50% of the nonischemic level, carvedilol increased coronary blood flow (49.4+/-5.6 to 73.5+/-7.5 mL x 100 g(-1) x min(-1); P<0.05) and adenosine release (112.3+/-22.2 to 240.6+/-57.1 nmol/L; P<0.05) during coronary hypoperfusion. This increase of coronary blood flow was attenuated by either 8-sulfophenyltheophylline or superoxide dismutase. In human umbilical vein endothelial cells cultured with or without xanthine and xanthine oxidase, carvedilol caused an increase of ecto-5'-nucleotidase activity. CONCLUSIONS: Carvedilol shows a cardioprotective effect against ischemia and/or reperfusion injury via adenosine-dependent mechanisms.

5'-Nucleotidase↗

PubMed2004

In vivo assessment of catechol O-methyltransferase activity in rabbit skeletal muscle.

With the use of microdialysis technique in the anesthetized rabbit, we examined the catechol O-methyltransferase (COMT) activity at the skeletal muscle interstitium. We implanted a dialysis probe into the adductor muscle, and monitored dialysate catecholamines and their metabolites with chromatogram-electrochemical detection. Administration of COMT inhibitor (entacapone) decreased dialysate 3-methoxy 4-hydroxyphenylglycol (MHPG) levels. Local administration of dihydroxyphenylglycol induced increases in dialysate MHPG levels. These increases in dialysate MHPG levels were suppressed by the addition of entacapone. The concentration of MHPG in the skeletal muscle dialysate corresponded to the COMT activity in the skeletal muscle. Furthermore, local administration of norepinephrine or epinephrine increased normetanephrine or metanephrine levels in dialysate but not MHPG levels. Skeletal muscle microdialysis with local administration of catecholamine offers a new method for in vivo assessment of regional COMT activity.

Animals↗

PubMed2004

Role of calcineurin B homologous protein in pH regulation by the Na+/H+ exchanger 1: tightly bound Ca2+ ions as important structural elements.

We studied the role of the interaction of calcineurin homologous protein 1 (CHP1) with the Na(+)/H(+) exchanger 1 (NHE1), particularly its EF-hand Ca(2+) binding motifs, in the intracellular pH (pH(i))-dependent regulation of NHE1. We found that (45)Ca(2+) binds to two EF-hand motifs (EF3 and 4) of the recombinant CHP1 proteins with high affinity (apparent K(d) = approximately 90 nM). Complex formation between CHP1 and the CHP1 binding domain of NHE1 resulted in a marked increase in the Ca(2+) binding affinity (K(d) = approximately 2 nM) by promoting a conformational change of the EF-hands toward the tightly Ca(2+)-bound form. This suggests that CHP1 always contains two Ca(2+) ions when associated with NHE1 in cells. Interestingly, overexpression of GFP-tagged CHP1 with mutations in EF3 or EF4 significantly reduced the exchange activity in the neutral pH(i) range and partly impaired the activation of NHE1 in response to various stimuli, such as growth factors and osmotic stress. Furthermore, we found that, in addition to reducing the activity (V(max)), a CHP1 binding-defective NHE1 mutant had a marked reduction in pH(i) sensitivity ( approximately 0.7 pH unit acidic shift), which consequently abolished various regulatory responses of NHE1. These observations suggest that the association of NHE1 with CHP1 is crucial for maintenance of the pH(i) sensitivity of NHE1 and that tightly bound Ca(2+) ions may serve as important structural elements in the "pH(i) sensor" of NHE1.

Animals↗

PubMed2004

Effects of Ca2+ channel antagonists on acetylcholine and catecholamine releases in the in vivo rat adrenal medulla.

To elucidate the types of voltage-dependent Ca(2+) channels controlling ACh and catecholamine releases in the in vivo adrenal medulla, we implanted microdialysis probes in the left adrenal medulla of anesthetized rats and investigated the effects of Ca(2+) channel antagonists on ACh, norepinephrine, and epinephrine releases induced by nerve stimulation. The dialysis probes were perfused with Ringer solution containing a cholinesterase inhibitor, neostigmine. The left splanchnic nerves were electrically stimulated at 2 and 4 Hz before and after intravenous administration of Ca(2+) channel antagonists. omega-Conotoxin GVIA (an N-type Ca(2+) channel antagonist, 10 microg/kg) inhibited ACh release at 2 and 4 Hz by approximately 40%, norepinephrine release at 4 Hz by approximately 50%, and epinephrine release at 2 and 4 Hz by approximately 45%. A fivefold higher dose of omega-conotoxin GVIA (50 microg/kg) did not further inhibit these releases. omega-Conotoxin MVIIC (a P/Q-type Ca(2+) channel antagonist, 50 microg/kg) inhibited ACh and epinephrine releases at 4 Hz by approximately 30%. Combined omega-conotoxin GVIA (50 microg/kg) and MVIIC (250 microg/kg) inhibited ACh release at 2 and 4 Hz by approximately 70% and norepinephrine and epinephrine releases at 2 and 4 Hz by approximately 80%. Nifedipine (an L-type Ca(2+) channel antagonist, 300 and 900 microg/kg) did not change ACh release at 2 and 4 Hz; however, nifedipine (300 microg/kg) inhibited epinephrine release at 4 Hz by 20%, and nifedipine (900 microg/kg) inhibited norepinephrine and epinephrine releases at 4 Hz by 30%. In conclusion, both N- and P/Q-type Ca(2+) channels control ACh release on preganglionic splanchnic nerve endings while L-type Ca(2+) channels do not. L-type Ca(2+) channels are involved in norepinephrine and epinephrine releases on chromaffin cells.

Acetylcholine↗

PubMed2004

Adrenomedullin gene transfer induces therapeutic angiogenesis in a rabbit model of chronic hind limb ischemia: benefits of a novel nonviral vector, gelatin.

BACKGROUND: Earlier studies have shown that adrenomedullin (AM), a potent vasodilator peptide, has a variety of cardiovascular effects. However, whether AM has angiogenic potential remains unknown. This study investigated whether AM gene transfer induces therapeutic angiogenesis in chronic hind limb ischemia. METHODS AND RESULTS: Ischemia was induced in the hind limb of 21 Japanese White rabbits. Positively charged biodegradable gelatin was used to produce ionically linked DNA-gelatin complexes that could delay DNA degradation. Human AM DNA (naked AM group), AM DNA-gelatin complex (AM-gelatin group), or gelatin alone (control group) was injected into the ischemic thigh muscles. Four weeks after gene transfer, significant improvements in collateral formation and hind limb perfusion were observed in the naked AM group and AM-gelatin group compared with the control group (calf blood pressure ratio: 0.60+/-0.02, 0.72+/-0.03, 0.42+/-0.06, respectively). Interestingly, hind limb perfusion and capillary density of ischemic muscles were highest in the AM-gelatin group, which revealed the highest content of AM in the muscles among the three groups. As a result, necrosis of lower hind limb and thigh muscles was minimal in the AM-gelatin group. CONCLUSIONS: AM gene transfer induced therapeutic angiogenesis in a rabbit model of chronic hind limb ischemia. Furthermore, the use of biodegradable gelatin as a nonviral vector augmented AM expression and thereby enhanced the therapeutic effects of AM gene transfer. Thus, gelatin-mediated AM gene transfer may be a new therapeutic strategy for the treatment of peripheral vascular diseases.

Adrenomedullin↗

PubMed2004

Effects of adrenomedullin inhalation on hemodynamics and exercise capacity in patients with idiopathic pulmonary arterial hypertension.

BACKGROUND: Adrenomedullin (AM) is a potent pulmonary vasodilator peptide. However, whether intratracheal delivery of aerosolized AM has beneficial effects in patients with idiopathic pulmonary arterial hypertension remains unknown. Accordingly, we investigated the effects of AM inhalation on pulmonary hemodynamics and exercise capacity in patients with idiopathic pulmonary arterial hypertension. METHODS AND RESULTS: Acute hemodynamic responses to inhalation of aerosolized AM (10 microg/kg body wt) were examined in 11 patients with idiopathic pulmonary arterial hypertension during cardiac catheterization. Cardiopulmonary exercise testing was performed immediately after inhalation of aerosolized AM or placebo. The work rate was increased by 15 W/min until the symptom-limited maximum, with breath-by-breath gas analysis. Inhalation of AM produced a 13% decrease in mean pulmonary arterial pressure (54+/-3 to 47+/-3 mm Hg, P<0.05) and a 22% decrease in pulmonary vascular resistance (12.6+/-1.5 to 9.8+/-1.3 Wood units, P<0.05). However, neither systemic arterial pressure nor heart rate was altered. Inhalation of AM significantly increased peak oxygen consumption during exercise (peak o(2), 14.6+/-0.6 to 15.7+/-0.6 mL. kg(-1). min(-1), P<0.05) and the ratio of change in oxygen uptake to that in work rate (Deltao(2)/DeltaW ratio, 6.3+/-0.4 to 7.0+/-0.5 mL. min(-1). W(-1), P<0.05). These parameters remained unchanged during placebo inhalation. CONCLUSIONS: Inhalation of AM may have beneficial effects on pulmonary hemodynamics and exercise capacity in patients with idiopathic pulmonary arterial hypertension.

Administration, Inhalation↗

PubMed2004

Simultaneous monitoring of acetylcholine and catecholamine release in the in vivo rat adrenal medulla.

To simultaneously monitor acetylcholine release from pre-ganglionic adrenal sympathetic nerve endings and catecholamine release from post-ganglionic adrenal chromaffin cells in the in vivo state, we applied microdialysis technique to anesthetized rats. Dialysis probe was implanted in the left adrenal medulla and perfused with Ringer's solution containing neostigmine (a cholinesterase inhibitor). After transection of splanchnic nerves, we electrically stimulated splanchnic nerves or locally administered acetylcholine through dialysis probes for 2 min and investigated dialysate acetylcholine, choline, norepinephrine and epinephrine responses. Acetylcholine was not detected in dialysate before nerve stimulation, but substantial acetylcholine was detected by nerve stimulation. In contrast, choline was detected in dialysate before stimulation, and dialysate choline concentration did not change with repetitive nerve stimulation. The estimated interstitial acetylcholine levels and dialysate catecholamine responses were almost identical between exogenous acetylcholine (10 microM) and nerve stimulation (2 Hz). Dialysate acetylcholine, norepinephrine and epinephrine responses were correlated with the frequencies of electrical nerve stimulation, and dialysate norepinephrine and epinephrine responses were quantitatively correlated with dialysate acetylcholine responses. Neither hexamethonium (a nicotinic receptor antagonist) nor atropine (a muscarinic receptor antagonist) affected the dialysate acetylcholine response to nerve stimulation. Microdialysis technique made it possible to simultaneously assess activities of pre-ganglionic adrenal sympathetic nerves and post-ganglionic adrenal chromaffin cells in the in vivo state and provided quantitative information about input-output relationship in the adrenal medulla.

Acetylcholine↗

PubMed2004

Methotrexate and MX-68, a new derivative of methotrexate, limit infarct size via adenosine-dependent mechanisms in canine hearts.

Methotrexate, an anti-rheumatic agent, has recently been reported to show an anti-inflammatory action via ecto-5'-nucleotidase- and adenosine-dependent mechanisms. Because ecto-5'-nucleotidase contributes to the production of adenosine and adenosine has a potent cardioprotective effect against ischemia/reperfusion injury, we investigated whether methotrexate or MX-68 [N-1-((2,4-diamino-6-pteridinyl) methyl)-3,4-dihydro-2H-1,4-benzothiazine-7- carbonyl]-N-2- aminoadipic acid] could reduce infarct size via adenosine-dependent mechanisms. In beagle dogs, the left anterior descending coronary artery was perfused through a bypass tube, which was occluded for 90 minutes followed by 6 hours of reperfusion. The size of infarcts was assessed by TTC staining. MX-68 reduced infarct size compared with that in untreated dogs (13.7 +/- 1.9 versus 38.6 +/- 5.3%, P < 0.01). This effect was completely blunted by either the adenosine receptor antagonist 8-sulfophenyltheophylline (8-SPT) (45.0 +/- 4.6% and 46.8 +/- 5.8% in the 8-SPT and MX-68 + 8-SPT groups, respectively) or by the ecto-5'-nucleotidase inhibitoralpha,beta-methylenadenosine 5'-diphosphate (AMP-CP) (44.0 +/- 4.5% and 46.7 +/- 5.8% in the AMP-CP and MX-68 + AMP-CP groups, respectively). Methotrexate also reduced infarct size to a level comparable with that in the MX-68 group, and its effect was also blunted by 8-SPT. There were no significant differences of collateral blood flow or risk area between the groups. We conclude that methotrexate and its derivative (MX-68) both limit infarct size via adenosine-dependent mechanisms.

2-Aminoadipic Acid↗

PubMed2004

Demonstration of enhanced K-edge angiography using a cerium target x-ray generator.

The cerium target x-ray generator is useful in order to perform enhanced K-edge angiography using a cone beam because K-series characteristic x rays from the cerium target are absorbed effectively by iodine-based contrast mediums. The x-ray generator consists of a main controller, a unit with a Cockcroft-Walton circuit and a fixed anode x-ray tube, and a personal computer. The tube is a glass-enclosed diode with a cerium target and a 0.5-mm-thick beryllium window. The maximum tube voltage and current were 65 kV and 0.4 mA, respectively, and the focal-spot sizes were 1.0 x 1.3 mm. Cerium Kalpha lines were left using a barium sulfate filter, and the x-ray intensity was 0.48 microC/kg at 1.0 m from the source with a tube voltage of 60 kV, a current of 0.40 mA, and an exposure time of 1.0 s. Angiography was performed with a computed radiography system using iodine-based microspheres. In coronary angiography of nonliving animals, we observed fine blood vessels of approximately 100 microm with high contrasts.

Angiography↗

PubMed2003

Detection of 3-methoxy-4-hydroxyphenylglycol in rabbit skeletal muscle microdialysate.

A high-performance liquid chromatography with electrochemical detection (HPLC-ED) method is described for determination of 3-methoxy-4-hydroxyphenylglycol (MHPG) in microdialysate from the skeletal muscle interstitial space. Using a microdialysis technique, we sampled 30 microl dialysate from the skeletal muscle interstitial space and injected dialysate directly into HPLC-ED system. The control MHPG concentration of dialysate was 213+/-18 pg/ml. The MHPG concentrations were reduced by entacapone (catechol-O-methyltransferase inhibitor, COMT), augmented by local infusion of dihydroxyphenylglycol. This system offers a new possibility for simple, rapid monitoring of MHPG as an index of COMT activity in skeletal muscle.

Animals↗

PubMed2003

Inhibition of cholinesterase elicits muscarinic receptor-mediated synaptic transmission in the rat adrenal medulla.

To determine the role of acetylcholinesterase in cholinergic synaptic transmission in the adrenal medulla in vivo, we applied a dialysis technique to the adrenal medulla of anesthetized rats and examined the effect of acetylcholinesterase inhibitor on the contribution of nicotinic and muscarinic receptors to catecholamine release. Exogenous acetylcholine-induced epinephrine release was inhibited by atropine (a muscarinic receptor antagonist) as well as hexamethonium (a nicotinic receptor antagonist). Endogenous acetylcholine (nerve stimulation)-induced epinephrine release was inhibited by hexamethonium but not atropine. In the presence of neostigmine (an acetylcholinesterase inhibitor), both exogenous and endogenous acetylcholine-induced catecholamine release was enhanced. In either case, epinephrine release was inhibited by atropine as well as hexamethonium. In the presence of eserine (another acetylcholinesterase inhibitor), endogenous acetylcholine-induced epinephrine release was also inhibited by atropine. Exogenous or endogenous acetylcholine-induced norepinephrine release was primarily inhibited by hexamethonium regardless of whether neostigmine was absent or present. In the rat adrenal medulla, the inhibition of acetylcholinesterase not only enhanced cholinergic synaptic transmission but also elicited muscarinic receptor-mediated synaptic transmission for epinephrine release.

Acetylcholinesterase↗

PubMed2003

Hybrid cell-gene therapy for pulmonary hypertension based on phagocytosing action of endothelial progenitor cells.

BACKGROUND: Circulating endothelial progenitor cells (EPCs) migrate to injured vascular endothelium and differentiate into mature endothelial cells. We investigated whether transplantation of vasodilator gene-transduced EPCs ameliorates monocrotaline (MCT)-induced pulmonary hypertension in rats. METHODS AND RESULTS: We obtained EPCs from cultured human umbilical cord blood mononuclear cells and constructed plasmid DNA of adrenomedullin (AM), a potent vasodilator peptide. We used cationic gelatin to produce ionically linked DNA-gelatin complexes. Interestingly, EPCs phagocytosed plasmid DNA-gelatin complexes, which allowed nonviral, highly efficient gene transfer into EPCs. Intravenously administered EPCs were incorporated into the pulmonary vasculature of immunodeficient nude rats given MCT. Transplantation of EPCs alone modestly attenuated MCT-induced pulmonary hypertension (16% decrease in pulmonary vascular resistance). Furthermore, transplantation of AM DNA-transduced EPCs markedly ameliorated pulmonary hypertension in MCT rats (39% decrease in pulmonary vascular resistance). MCT rats transplanted with AM-expressing EPCs had a significantly higher survival rate than those given culture medium or EPCs alone. CONCLUSIONS: Umbilical cord blood-derived EPCs had a phagocytosing action that allowed nonviral, highly efficient gene transfer into EPCs. Transplantation of AM gene-transduced EPCs caused significantly greater improvement in pulmonary hypertension in MCT rats than transplantation of EPCs alone. Thus, a novel hybrid cell-gene therapy based on the phagocytosing action of EPCs may be a new therapeutic strategy for the treatment of pulmonary hypertension.

Adrenomedullin↗

PubMed2003

Biodegradable gelatin hydrogel potentiates the angiogenic effect of fibroblast growth factor 4 plasmid in rabbit hindlimb ischemia.

OBJECTIVES: We investigated the potentiation of gene therapy using fibroblast growth factor 4 (FGF4)-gene by combining plasmid deoxyribonucleic acid (DNA) with biodegradable gelatin hydrogel (GHG). BACKGROUND: Virus vectors transfer genes efficiently but are biohazardous, whereas naked DNA is safer but less efficient. Deoxyribonucleic acid charges negatively; GHG has a positively charged structure and is biodegradable and implantable; FGF4 has an angiogenic ability. METHODS: The GHG-DNA complex was injected into the hindlimb muscle (63 mice and 55 rabbits). Gene degradation was evaluated by using (125)I-labeled GHG-DNA complex in mice. Transfection efficiency was evaluated with reverse-transcription nested polymerase chain reaction and X-Gal histostaining. The therapeutic effects of GHG-FGF4-gene complex (GHG-FGF4) were evaluated in rabbits with hindlimb ischemia. RESULTS: Gelatin hydrogel maintained plasmid in its structure, extending gene degradation temporally until 28 days after intramuscular delivery, and improving transfection efficiency. Four weeks after gene transfer, hindlimb muscle necrosis was ameliorated more markedly in the GHG-FGF4 group than in the naked FGF4-gene and GHG-beta-galactosidase (control) groups (p < 0.05, Kruskal-Wallis test). Synchrotron radiation microangiography (spatial resolution, 20 microm) and flow determination with microspheres confirmed significant vascular responsiveness to adenosine administration in the GHG-FGF4 group, but not in the naked FGF4-gene and the control. CONCLUSIONS: The GHG-FGF4 complex promoted angiogenesis and blood flow regulation of the newly developed vessels possibly by extending gene degradation and improving transfection efficiency without the biohazard associated with viral vectors.

Absorbable Implants↗

PubMed2003

Effects of ketamine on exocytotic and non-exocytotic noradrenaline release.

To characterise ketamine-induced sympathomimetic action, we examined the effects of ketamine on in vivo cardiac sympathetic nerve endings function. Using adult cats given anaesthesia with pentobarbital, dialysis probes were implanted in the left ventricular myocardium and dialysate noradrenaline (NA) concentrations were measured as an indicator of NA output at the cardiac sympathetic nerve endings. Ketamine was locally administered through the dialysis probe, and dialysate NA responses were obtained in the following conditions. (1) In the resting state, ketamine (10 mM) increased dialysate NA concentration. This increase in dialysate NA was not altered by addition of omega-conotoxin GVIA (N-type Ca(2+) channel blocker) or desipramine (membrane NA uptake blocker). (2) Sympathetic activation by electrical stimulation of the stellate ganglia (ES-SG; exocytotic NA release): ES-SG caused an increase in dialysate NA, which was further augmented by addition of desipramine. During co-administration of desipramine and ketamine, dialysate NA response to ES-SG was smaller than with desipramine alone. Further, there was no significant difference in the dialysate NA response to ES-SG between ketamine and ketamine + desipramine. These data suggested that both exocytosis and NA uptake function were impaired by ketamine. (3) Non-exocytotic NA release by ouabain: ouabain caused increases in dialysate NA. These increases in dialysate NA were suppressed by ketamine, which impaired the membrane outward NA transport evoked by ouabain. We conclude that ketamine impaired exocytotic and non-exocytotic NA release. However, ketamine spontaneously evoked NA efflux that was independent of exocytosis and insensitive to NA transporter.

Animals↗

PubMed2003

In vivo monitoring of norepinephrine and its metabolites in skeletal muscle.

Although skeletal muscle sympathetic nerve activity plays an important role in the regulation of vascular tone and glucose metabolism, relatively little is known about regional norepinephrine (NE) kinetics in the skeletal muscle. With use of the dialysis technique, we implanted dialysis probes in the adductor muscle of anesthetized rabbits and examined whether dialysate NE and its metabolites were influenced by local administration of pharmacological agents through the dialysis probes. Dialysate dihydroxyphenylglycol (DHPG) and 3-methoxy-4-hydroxyphenylglycol (MHPG) were measured as two major metabolites of NE. The skeletal muscle dialysate NE, DHPG and MHPG were 11.7+/-1.2, 38.1+/-3.2, and 266.1+/-28.7 pg/ml, respectively. Basal dialysate NE levels were suppressed by tetrodotoxin (Na(+) channel blocker, 10 microM) (5.1+/-0.6 pg/ml), and augmented by desipramine (NE uptake blocker, 100 microM) (25.8+/-3.2 pg/ml). Basal dialysate DHPG levels were suppressed by pargyline (monoamine oxidase blocker, 1mM) (24.3+/-4.6 pg/ml) and augmented by reserpine (vesicle NE transport blocker, 10 microM) (75.8+/-2.7 pg/ml). Basal dialysate MHPG levels were not affected by pargyline, reserpine, or desipramine. Addition of tyramine (sympathomimetic amine, 600 microM), KCl (100 mM), and ouabain (Na(+)-K(+) ATPase blocker, 100 microM) caused brisk increases in dialysate NE levels (200.9+/-14.2, 90.6+/-25.7, 285.3+/-46.8 pg/ml, respectively). Furthermore, increases in basal dialysate NE levels were correlated with locally administered desipramine (10, 100 microM). Thus, dialysate NE and its metabolite were affected by local administration of pharmacological agents that modified sympathetic nerve endings function in the skeletal muscle. Skeletal muscle microdialysis with local administration of a pharmacological agent provides information about NE release, uptake, vesicle uptake and degradation at skeletal muscle sympathetic nerve endings.

Animals↗

PubMed2003

Changes in functional and histological distributions of nitric oxide synthase caused by chronic hypoxia in rat small pulmonary arteries.

1. Chronic hypoxia (CH) increases lung tissue expression of all types of nitric oxide synthase (NOS) in the rat. However, it remains unknown whether CH-induced changes in functional and histological NOS distributions are correlated in rat small pulmonary arteries. 2. We measured the effects of NOS inhibitors on the internal diameters (ID) of muscular (MPA) and elastic (EPA) pulmonary arteries (100-700 micro m ID) using an X-ray television system on anaesthetized rats. We also conducted NOS immunohistochemical localization on the same vessels. 3. Nonselective NOS inhibitors induced ID reductions in almost all MPA of CH rats (mean reduction, 36+/-3%), as compared to approximately 60% of control rat MPA (mean, 10+/-2%). The inhibitors reduced the ID of almost all EPA with similar mean values (approximately 26%) in both CH and control rats. On the other hand, inducible NOS (iNOS)-selective inhibitors caused ID reductions in approximately 60% of CH rat MPA (mean, 15+/-3%), but did so in only approximately 20% of control rat MPA (mean, 2+/-2%). This inhibition caused only a small reduction (mean, approximately 4%) in both CH and control rat EPA. A neuronal NOS-selective inhibitor had no effect. 4. The percentage of endothelial NOS (eNOS)-positive vessels was approximately 96% in both MPA and EPA from CH rats, whereas it was 51 and 91% in control MPA and EPA, respectively. The percentage for iNOS was approximately 60% in both MPA and EPA from CH rats, but was only approximately 8% in both arteries from control rats. 5. The data indicate that in CH rats, both functional and histological upregulation of eNOS extensively occurs within MPA. iNOS protein increases sporadically among parallel-arranged branches in both MPA and EPA, but its vasodilatory effect is predominantly observed in MPA. Such NOS upregulation may serve to attenuate hypoxic vasoconstriction, which occurs primarily in MPA and inhibit the progress of pulmonary hypertension.

Animals↗

PubMed2003

Acute limb ischemia does not facilitate but inhibits norepinephrine release from muscle sympathetic nerve endings in anesthetized rabbit.

Although myocardial ischemia is associated with regional cardiac sympathetic nerve deterioration, it remains unknown whether acute hindlimb ischemia impairs muscle sympathetic nerve function. In the study presented here we implanted dialysis probes in the adductor muscle of anesthetized rabbits and measured dialysate norepinephrine levels as an index of muscle sympathetic nerve activity. Acute hindlimb ischemia was induced by injection of microspheres and occlusion of the common iliac artery. Dialysate norepinephrine levels decreased from 19.3 +/- 3.5 pg/ml at control to 9.4 +/- 3.7 pg/ml at 30 min of ischemia and further to 1.7 +/- 0.2 pg/ml at 75 min of ischemia. During acute hindlimb ischemia, baroreflex (bilateral carotid occlusion) and high potassium level-induced norepinephrine response was inhibited, but tyramine-induced norepinephrine response was preserved. In conclusion, acute hindlimb ischemia caused decreases in dialysate norepinephrine levels. This reduction may be mediated by an impairment of axonal conduction and/or of norepinephrine releasing function at skeletal muscle sympathetic nerve endings.

Adrenergic Fibers↗