Structure of the TCR expressed on a gastritogenic T cell clone, II-6, and frequent appearance of similar clonotypes in mice bearing autoimmune gastritis

A parietal cell-specific Th1 clone, II-6, which was established from a BALB/c mouse bearing post-thymectomy autoimmune gastritis (AIG), recognizes a peptide of the alpha subunit (alpha891-905) of H+/K+-ATPase and induces gastritis in nu/nu BALB/c mice by adoptive cell transfer. In the present study, the primary structure of the TCR of II-6 was determined as Valpha10-Jalpha c5a-Calpha and Vbeta14-Jbeta2.3-Cbeta2 by cDNA cloning. Using PCR with specific primers, we defined the use of this II-6 TCR in nu/nu mice with transferred II-6 cells and in mice that spontaneously developed AIG by thymectomy on day 3 after birth (d3-Tx). II-6 TCR mRNAs were detected in the gastric mucosa of all of the nu/nu mice, suggesting that II-6 cells indeed home to the gastric mucosa and thereby were directly involved in the destruction of target parietal cells. TCR beta chain mRNAs encoding CDR3 region sequences almost identical with that of II-6 were also found in the gastric mucosa in 43% (six of 14 mice tested) of the d3-Tx AIG mice at 4-12 weeks old by nested RT-PCR. Such a frequent appearance of similar clonotypes in independent individuals suggests that T cells bearing II-6-like TCR including the II-6 itself might be directly involved in, although not essential for, the pathogenesis of AIG in 3d-Tx mice.

Comparative studies of antimitochondrial autoantibodies in sera and bile in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune liver disease characterized by destruction of intrahepatic bile ducts. Although the pathogenesis of this disease is still unknown, high titers of antimitochondrial autoantibodies (AMA) have long been recognized in patient sera. However, little is known about the presence of AMA in bile. In this study, we investigated bile and sera from patients with PBC and healthy controls for the presence of AMA and mitochondrial autoantigens. AMA were detected in the bile of 17 of 19 patients (89.4%) with PBC; they were specifically directed against the pyruvate dehydrogenase complex (PDC-E2) in 15 of 19 patients (78.9%), to the branched-chain 2-oxo-acid dehydrogenase complex E2 (BCOADC-E2) in 6 of 19 patients (31.6%), and to the 2-oxoglutarate dehydrogenase complex E2 (OGDC-E2) in 1 of 19 patients (5.3%). In a comparative study of sera from the same patients, anti-PDC-E2 antibodies were found in 19 of 19 patients (100%), anti-BCOADC in 9 of 19 patients (47.3%), and anti-OGDC-E2 in 4 of 19 patients (21.1%) patients. AMA in bile were always found together with antibodies of corresponding specificities in the serum from the same patient. Immunoglobulin (Ig)A AMA were found in the bile of 9 of 19 patients (47.7%) with PBC; they were specifically directed against PDC-E2 in 8 of 19 patients (42.1%) and to BCOADC in 2 of 19 patients (10.5%). Epitope mapping of IgA anti-PDC-E2 antibodies indicated that, like serum autoantibodies, the immunodominant epitope is directed against the inner lipoyl domain of PDC-E2. The prevalence and antigen reactivity of IgA AMA in sera correlated completely with IgA AMA in bile. Autoantibodies against nuclear envelope pore proteins (gp210) were found in 1 of 8 (12.5%) sera of patients with PBC, but not in bile. Furthermore, and of particular interest, we detected the autoantigens, PDC-E2, OGDC-E2, and BCOADC-E2, in the bile of 12 of 19 patients (63.2%), 9 of 19 patients (47.4%), and 9 of 19 patients (47.4%), respectively; PDC-E2 was found in only 1 of 17 (5.9%) disease controls. Although the presence of AMA in bile may merely reflect the presence of these antibodies in sera, the simultaneous detection of mitochondrial autoantigens in bile suggests an increase of mitochondrial autoantigens at inflammatory sites. Such autoantigens, coupled with AMA, may augment the local immune response and disease progression.

Cyclothialidine analogs, novel DNA gyrase inhibitors

DNA gyrase inhibitors, cyclothialidines B, C, D and E were isolated from four Streptomycete strains (NR 0659, NR 0660, NR 0661 and NR 0662). Their structures have been elucidated based on the amino acid analysis of the hydrolysates, NMR and HRFAB-MS experiments and shown to be cyclothialidine analogs. The absolute stereochemistry has been determined by the chiral HPLC analysis of the hydrolysates. Cyclothialidines B, D and E are novel and potent inhibitors of DNA gyrase.

Ex vivo study of the increased sensitivity to NO of endothelium-denuded thoracic aortas isolated from dietary magnesium-deficient rats

The mechanisms underlying the enhanced relaxant responses to sodium nitroprusside (SNP) associated with magnesium (Mg) deficiency were examined using endothelium-denuded thoracic aortas isolated from rats with dietary Mg deficiency. This enhancement of SNP-induced relaxation was abolished or depressed in the presence of methylene blue (a guanylate cyclase inhibitor). The relaxant responses to 8-bromo cyclic GMP (8-Br cGMP; a membrane-permeable cGMP) of thoracic aortas isolated from Mg-deficient rats were enhanced like those to SNP. These enhanced relaxant responses were depressed by tetraethylammonium (a non-specific K+ channel blocker). Charybdotoxin, a large conductance Ca2+-activated K+ (K[Ca]) channel blocker, inhibited 8-Br cGMP-induced relaxations of aortas from Mg-deficient and control rats. Apamin, a small conductance K(Ca) channel blocker, inhibited 8-Br cGMP-induced relaxations of aortas from Mg-deficient, but not control rats. The relaxant responses to cromakalim (an ATP-sensitive K+ channel opener) of the two groups were not significantly different. These ex vivo results show that dietary Mg deficiency in rats leads to increased sensitivity to NO of endothelium-denuded thoracic aortas in vitro and K(Ca) channel activation via cGMP may be involved in this enhancement.

Ex vivo study of the effects of dietary magnesium deficiency on the formation and release of NO from endothelial cells and the sensitivity to NO of smooth muscle cells of thoracic aortas isolated from rats

We found that the contractile responses to phenylephrine (PE) of isolated endothelium-intact thoracic aortas were enhanced by a nitric oxide (NO) synthase inhibitor, nitro-L-arginine (LNAG). and the magnitude of this enhancement was significantly greater in Mg-deficient than control rats. In this study, we used a sandwich method to evaluate the effects of dietary Mg deficiency on the ability of vascular endothelial cells to form and/or release NO and on the sensitivity to NO of vascular smooth muscle cells. Male Wistar rats were fed a Mg-deficient (10 mg Mg/kg diet) or control (700 mg Mg/kg diet) diet for 30 days. With the sandwich method, when endothelium-denuded thoracic aortas from chow fed rats were used as the assay vessels, and endothelium-intact aortas from control or Mg-deficient rats were used as the NO-donor vessels, neither the aortic contractile responses to PE nor the enhancement by LNAG of these responses in control and Mg-deficient rats differed significantly. When endothelium-denuded thoracic aortas from control or Mg deficient rats were used as the assay vessels and endothelium-intact aortas from chow fed rats were used as NO-donor vessels, LNAG enhanced PE-induced contractions to a significantly greater extent in Mg-deficient than control rats. Furthermore, sodium nitroprusside (a NO donor) had a greater relaxant effect on endothelium-denuded thoracic aortas isolated from Mg-deficient than control rats. These ex vivo results suggest that dietary Mg deficiency in rats has little effect on the formation and/or release of NO by aortic endothelial cells. but it does appear to increase the sensitivity to NO of aortic smooth muscle cells.

A possible involvement of Fas-Fas ligand signaling in the pathogenesis of murine autoimmune gastritis

BACKGROUND & AIMS

A Th1 clone, II-6, established from an autoimmune gastritis BALB/c mouse that underwent thymectomy 3 days after birth, recognized a 15 mer peptide constructing the alpha subunit of H+, K(+)-adenosine triphosphatase as antigen and induced gastritis in nu/nu mice by adoptive transfer. The aim of this study was to examine the molecular mechanism of target (parietal cells) destruction in either thymectomized or II-6 cell-transferred nu/nu mice.

METHODS

Expression of Fas, major histocompatibility complex class II, and intercellular adhesion molecule 1 molecules on the gastric mucosa of these mice were immunohistochemically examined. In situ DNA fragmentation in these thymectomized or nu/nu mice was tested by the terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine triphosphate nick end label (TUNEL) method. Moreover, activity of II-6 cells to induce apoptosis was tested by using the 15 mer peptide-pulsed B lymphoma cells, A20.2J, as the target.

RESULTS

A portion of parietal cells in gastritis-bearing thymectomized or nu/nu mice at an early stage expressed Fas, major histocompatibility complex class II, and intercellular adhesion molecule 1 molecules and was TUNEL positive. Fas-ligand message was induced on activated II-6 cells and caused DNA fragmentation of the antigen-pulsed A20.2J cells.

CONCLUSIONS

Cognate interaction between Fas antigen on the target and Fas ligand on the effector seems to be one possible mechanism for the target cell destruction in organ-specific autoimmune gastritis.

Stability of free Mg2+ concentration and increased concentration of free Ca2+ in vascular smooth muscle cells during dietary magnesium deficiency in rat

Intracellular free calcium and magnesium ion concentrations ([Ca2+]i and [Mg2+]i respectively) were estimated in thoracic aorta smooth muscle strips isolated from magnesium-deficient and control rats using fura-2/AM and mag-fura-2/AM, respectively. Adult male Wistar rats were fed a magnesium-deficient diet (10 mg Mg/kg diet) or a control diet (700 mg Mg/kg diet) for 30 days. Plasma magnesium level in magnesium-deficient rats was half of that in control rats at 30th day. Therefore, thoracic aorta strips, denuded of endothelium, were loaded with fura-2/AM or mag-fura-2/AM in the presence of 0.5 or 1.0 mM Mg2+, and [Ca2+]i or [Mg2+]i was measured under the same Mg2+ conditions. The [Ca2+]i in the aorta strips isolated from magnesium-deficient rats in the presence of 0.5 mM Mg2+ (254.9 +/- 13.1 nM) was approximately three times greater than in those from control rats in the presence of 1.0 mM Mg2+ (86.5 +/- 9.2 nM). The [Mg2+]i was not significantly different between the two groups at either Mg2+ level. The muscle tension and [Ca2+]i increased after [Mg2+]o was exchanged from 1.0 to 0.5 mM; however, [Mg2+]i showed no change. The total calcium content increased and total magnesium content decreased in thoracic aorta strips isolated from magnesium-deficient rats. These results suggest that [Mg2+]i is stable, but that [Ca2+]i increases in vascular smooth muscle cells of thoracic aortas isolated from dietary magnesium-deficient rats.

[A case report of transaortic mitral valve replacement in Marfan's syndrome]

One-stage operation was successfully performed in 30-year-old male with annulo aortic ectasia and mitral valve regurgitation secondary to Marfan's syndrome. The replacement of the mitral valve was performed through aortic root. The transaortic mitral valve replacement employed here should prove useful for similar cases requiring reconstruction of aortic root and replacement of mitral valve simultaneously in Malfan's syndrome.

The vasomotor effects of 5-hydroxytryptamine on equine basilar arteries in vitro

The vasomotor effects of 5-hydroxytryptamine (5-HT) on isolated equine basilar arteries were studied. 5-HT induced contractions of equine basilar arteries in a concentration-dependent manner, with a pEC50 value (with 95% confidence limits) of 7.35 (7.08-7.62). Similar results were obtained with endothelium-denuded basilar arteries. Contractions were not competitively inhibited by the 5-HT2 receptor antagonist ketanserin at low concentrations of 5-HT. Conversely, at high concentrations of 5-HT, contractions were inhibited by ketanserin in a concentration-dependent manner, with a pA2 value of 8.91 (8.62-9.20). The 5-HT1 and 5-HT2 receptor antagonist methiothepin shifted the concentration-response curve of 5-HT downwards and to the right in a concentration-dependent manner. In the presence of 10(-6) mol/L ketanserin, however, methiothepin antagonized 5-HT-induced contractions competitively with a pA2 value of 7.95 (7.59-8.31). The 5-HT3 receptor antagonist MDL 72222 had no effect on 5-HT-induced contractions. The findings of this study indicate that 5-HT1 and 5-HT2 receptors are located in equine basilar arterial smooth muscle cells, and that stimulation of these receptors results in contraction.

Myasthenia gravis, acute transverse myelitis, and HTLV-I

We present the unusual case of a 49-year-old female carrier of HTLV-I with myasthenia gravis who presented with acute transverse myelitis. Laboratory data suggested a recent infection with varicella zoster virus and demyelination by an autoimmune process in the central nervous system. Adult T-cell leukemia-like cells were observed in the cerebrospinal fluid. T-cell-mediated immune responses modulated by HTLV-I infection may be involved in the pathogenesis of myasthenia gravis and acute transverse myelitis in this case.

Breakdown of self-tolerance by intrathymic injection of a T-cell line inducing autoimmune gastritis in mice

Autoimmune gastritis (AIG) develops spontaneously in BALB/c mice thymectomized 3 days after birth (3d-Tx). We first confirmed our previous observations that CD4+ splenic T cells in AIG mice induced AIG in nu/nu mice, while those in normal mice suppressed the development of the disease. In addition, we found that a quantitative balance between these effector (Te) and suppressor (Ts) T cells determined either onset or prevention of the disease. Peripheralization of Ts seemed to begin around 3 days after birth, since the incidence of AIG in mice that underwent Tx 6 days after birth (6d-Tx) decreased markedly, compared with that of 3d-Tx mice; 12% in the former, while 79% in the latter. Notably, Ts existed in the 6d-Tx mice that escaped AIG. We next examined the target specificity of such Ts using syngeneic parietal cells known as autoantigens and two kinds of T-cell lines established from an AIG mouse; one is gastritis inducible in vivo, termed A-II, while another is not, named AC-II. Intrathymic injection of parietal cells into mice 3 days after birth followed by 6d-Tx completely prevented the development of AIG. In contrast, injection of irradiated A-II, but not AC-II cells resulted in AIG in 67% of the mice. No autoimmune oophoritis (AIO) was induced in female mice, implying that the breakdown of tolerance is organ specific. Taken together, peripheral tolerance for organ-specific autoantigens seems to be maintained by CD4+ Ts responding to Te, which induces the disease.

Responsiveness of equine basilar artery to transmural nerve stimulation differs from that of porcine and bovine basilar arteries in vitro

Transmural nerve stimulation (TNS) induced relaxations in porcine and bovine basilar arteries which were abolished by tetrodotoxin (TTX) and by L-nitro-arginine (LNAG). However, TNS induced contractions in equine basilar artery which were abolished by TTX and by guanethidine, but not by LNAG. These results suggest that the TNS-induced contractions of equine basilar arteries may be mediated by norepinephrine release.

[The effect of local transient cooling on anodermal blood flow]

To clarify the regulatory mechanism of blood flow of anodermal mucosal layers responding to the localized and transient coolong stimulation (around -4 degrees C), we examined the change of anodermal blood flow with use of Laser Doppler Flowmeter (Periflux, Perimed). The cooling stimulation was applied to anoderm by the insertion of chilled cold stick (Poscool, Maruho) into the anus of 11 healthy male volunteer, aged 20-25 years. Experimental results obtained are as follow; 1) The anodermal blood flow of healthy subjects are variant in degree and widely distributed from 30 to 80 Perfusion Unit (PU). 2) After cooling for five minutes by the insertion of a frozen Poscool, anodermal blood flow were increased in 8 cases out of eleven (72.7%). The changes corresponds to be 1.4 to 5.2 times. 3) Eight cases are divided into two groups on the basis of the time course after cooling: the one is "delayed responding group" (there is a delay 10-40 minutes before the blood flow is increasing) and the other is "rapid responding group" (the blood flow is immediately increasing). These results indicate that the anodermal blood flow, which are exposed to cooling, of healthy subjects is regulated not only by nervous mechanism but by humoral mechanism. Then, based on the Lewis reaction (cold vasodilatation), it is suggested that the short time cooling of anoderm should be appreciated as a conservative therapy of hemorrhoids and anal fissures.

Mechanisms of the enhanced contractile response to a low concentration of phorbol 12,13-dibutyrate in thoracic aorta isolated from rats with dietary magnesium deficiency

The mechanisms underlying the enhanced contractile response to phorbol 12,13-dibutyrate (PDBu) were examined in de-endothelialized thoracic aortas isolated from rats with dietary magnesium (Mg) deficiency. PDBu (1.0 nM)-induced contractions were significantly larger in Mg-deficient rats than in the controls. The contraction was completely inhibited by nifedipine, removal of external Ca2+ or by l-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7). PDBu (1.0 nM) and phorbol 12-myristate 13-acetate (1.0 microM) significantly decreased the KD value and increased the Bmax for the binding of [3H]PN200-110 to the aortas. The degree of the decrease in the KD value was significantly greater in Mg-deficient rats than in the controls. The PDBu-induced decrease in the KD value was abolished by H7. These results suggest that activation of protein kinase C by phorbol esters may participate in the activation of L-type Ca2+ channels, which increases both the affinity of [3H]PN200-110 binding and the magnitude of the external Ca(2+)-dependent contraction. Dietary Mg-deficiency may enhance these processes.

Enhanced contractile response to phenylephrine and increased density of [3H]PN200-110 binding sites in thoracic aorta isolated from dietary magnesium-deficient rats

The present study was undertaken to examine whether the enhanced contractile response to phenylephrine observed in thoracic aorta isolated from dietary magnesium-deficient rats depends on an increased density of alpha 1-adrenoceptor or calcium channels. Adult male Wistar rats were fed with a magnesium-deficient diet (0.001 per cent magnesium) for 30 days with control groups (0.07 per cent magnesium). The contractile response to phenylephrine was significantly inhibited by nifedipine in both aortas without endothelium, and the degree of the inhibition was significantly greater in magnesium-deficient rats than in controls. Membranes were isolated from both thoracic aortas without endothelium, and the binding of [3H]PN200-110 or [3H]prazosin to the membranes was studied. A single binding site for [3H]PN200-110 or [3H]prazosin was evident for both membranes with high affinity. Dietary magnesium-deficiency increased significantly the maximal number (Bmax) of [3H]PN200-110 binding sites, but not Bmax of [3H]prazosin, and did not alter the binding affinity of both ligands. These results suggest that increased density of calcium channels participates in the enhanced contractile response to phenylephrine in thoracic aortas isolated from dietary magnesium-deficient rats.

A conserved epitope on H+,K(+)-adenosine triphosphatase of parietal cells discerned by a murine gastritogenic T-cell clone

BACKGROUND/AIMS

H+,K(+)-adenosine triphosphatase (H+,K(+)-ATPase) of parietal cells is an organ-specific enzyme recognized by autoantibodies found in human and murine autoimmune gastritis (AIG). Murine AIG can be induced in BALB/c mice by thymectomy 3 days after birth and is a T cell-mediated disease. This study examined the specificity of T cells that cause AIG and the role of H+,K(+)-ATPase in this disease.

METHODS

From an AIG mouse, a gastritogenic T-cell clone (II-6) was established, and its reactivity to synthetic peptides of H+,K(+)-ATPase was tested.

RESULTS

II-6 cells are CD4+, V beta 14+, and interferon gamma producers. Adoptive transfer of II-6 cells to syngeneic nude mice resulted in AIG without the production of autoantibodies to parietal cells. The II-6 cells were responsive not only to murine but also to human and porcine parietal cells. Their proliferation was also induced by amino acids 891-905 (alpha 891) and 892-906 (alpha 892) of the alpha subunit of porcine and human H+,K(+)-ATPase, respectively.

CONCLUSIONS

The T-cell response to a single epitope of H+,K(+)-ATPase, the amino acid sequence of which is conserved among at least three mammals tested, is sufficient to cause AIG. Autoantibodies to parietal cells are not detected in these AIG mice.

Vasomotor effects of histamine on bovine and equine basilar arteries in vitro

The vasomotor effects of histamine on isolated bovine and equine basilar arteries were examined. Histamine induced contractions in both these preparations. The maximal response to and pEC50 value for histamine of the equine artery were larger than those of bovine tissue. Similar results were obtained with endothelium-denuded basilar arteries. Diphenhydramine (H1-receptor antagonist) inhibited histamine-induced contractions of the basilar arteries from both species in a concentration-dependent manner and its pA2 values (with 95% confidence limits) were 7.61 (7.39-7.83) and 8.15 (8.01-8.29) for the bovine and equine preparations, respectively. Cimetidine (H2-receptor antagonist) slightly potentiated histamine-induced contractions of bovine, but not equine, basilar arteries. 2-Thiazolylethylamine (H1-receptor agonist) induced contractions in both preparations, whereas impromidine (H2-receptor agonist) induced weak relaxation of the bovine, but not the equine, tissue. These findings indicate that bovine basilar arterial smooth muscle cells possess H1- and H2-receptors. Stimulation of the former results in contraction, whereas stimulation of the latter results in weak relaxation. Equine basilar arterial smooth muscle cells possess H1-receptors, stimulation of which results in contraction.

Endothelial modulation of vascular tone in isolated porcine and bovine basilar arteries

Endothelium-dependent modulation of vascular tone was investigated in isolated porcine and bovine basilar arteries. L-Nitro-arginine (NO synthase inhibitor) and methylene blue (soluble guanylate cyclase inhibitor) increased, but indomethacin (cyclooxygenase inhibitor) decreased the vascular tone in the basilar arteries from both species. Bradykinin evoked relaxation of precontracted porcine basilar artery, but not bovine basilar artery. Sodium fluoride (endothelial G-protein activator) produced relaxation of precontracted basilar arteries from both species. The effects of bradykinin and sodium fluoride were completely abolished by endothelial denudation and markedly inhibited by L-nitro-arginine and methylene blue, but not by indomethacin. Sodium nitroprusside (guanylate cyclase activator) evoked relaxation of precontracted endothelium-denuded basilar arteries from both species. These results suggest that there is species variation in endothelium-dependent modulation of vascular tone in the basilar artery.

Characterization of 5-hydroxytryptamine receptors on the isolated pig basilar artery by functional and radioligand binding studies

5-Hydroxytryptamine (5-HT)-receptor subtypes on pig basilar arteries were investigated by measuring the contractile responses to 5-HT agonists, the effects of antagonists on the responses and by carrying out a radioligand binding assay with [3H]5-HT. The rank order of contractile agonist potency (according to the pEC50 values) was 5-carboxamidotryptamine > or = 5-HT > alpha-methyl-5-HT > (+/-)-8-hydroxy-dipropylaminotetralin. The contractile responses were not affected by endothelial denudation, and the 5-HT-induced contractions were antagonized competitively by ketanserin. Methiothepin shifted the 5-HT concentration-response curves to the right and downwards in a concentration-dependent manner. In the presence of ketanserin (10(-6) M), however, methiothepin antagonized the 5-HT-induced contractions competitively. Specific [3H]5-HT binding to 5-HT receptors was saturable, reversible and showed high (Kd, 2.5 nM) and low (Kd, 710 nM) affinities, with respective Bmax values of 29.5 and 1950 fmol/mg protein. These results indicate that both 5-HT1 and 5-HT2 receptors are present on pig basilar arterial smooth muscle cells, and their stimulation results in contraction.

Equine coronary artery responds to 5-hydroxytryptamine with relaxation in vitro

Isolated equine coronary arteries responded to 5-hydroxytryptamine (5-HT) with relaxations in both endothelium-dependent and endothelium-independent mechanisms. Experiments were designed to characterize the 5-HT receptor subtype mediating these relaxations. Both 5-HT and alpha-methyl-5-HT (alpha-Me-5-HT; 5-HT2 agonist) produced concentration-dependent relaxations in equine coronary arteries precontracted with a thromboxane A2 derivative (ONO11113). The degree of the maximal relaxation induced by alpha-Me-5-HT was about one-half of that induced by 5-HT. In the coronary arteries without endothelium, alpha-Me-5-HT produced no relaxation, but 5-HT caused relaxation, which was inhibited by a 5-HT1 antagonist (methysergide, mianserin and methiothepin), but was inhibited neither by ketanserin (5-HT2 antagonist) nor by MDL72222 (5-HT3 antagonist). In the coronary arteries with endothelium, however, the relaxation induced by alpha-Me-5-HT was inhibited by ketanserin, L-nitro-arginine (NO synthase inhibitor) and methylene blue (soluble guanylate cyclase inhibitor). These results suggest that the relaxation induced by 5-HT in equine coronary arteries depends mainly on the stimulation of both 5-HT1 receptor subtype on smooth muscle cells directly, and 5-HT2 receptor subtype on endothelial cells indirectly by liberating endothelium-derived NO.

Characterization of muscarinic receptor subtype mediating contraction and relaxation in equine coronary artery in vitro

In coronary arterial rings isolated from horses, 10(-8)-10(-6) mol/l acetylcholine (ACh) induced concentration-dependent contractions which were potentiated by the removal of endothelium and by pretreatment with L-nitro-arginine (LNAG) or methylene blue (MB). Relatively lower concentrations of ACh (10(-14)-10(-8) mol/l) induced relaxation when the coronary rings were contracted by phenylephrine (PE). ACh-induced contractions in the coronary rings without endothelium were competitively inhibited by each muscarinic subtype selective antagonist in the following order of potency: 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) > pirenzepine > or = parafluoro-hexahydrosiladiphenidol (pFHHSiD) > methoctramine. ACh-induced relaxation in the rings with endothelium was inhibited by LNAG or MB, and by each selective antagonist in the following order of potency: 4-DAMP > pFHHSiD > pirenzepine > methoctramine. These results suggest that the ACh-induced contraction and relaxation in equine coronary arteries are mediated mainly by an M3-receptor located on the smooth muscle cells and endothelial cells, respectively, and that the stimulation of the M3-receptor on the endothelial cells liberates nitric oxide.

Mechanisms of the enhanced contractile response to phenylephrine in thoracic aorta isolated from rats with dietary magnesium deficiency

The mechanisms underlying the enhanced contractile response to phenylephrine (PE) and increased susceptibility to nifedipine of de-endothelialized thoracic aorta isolated from rats with dietary magnesium deficiency (Mg-deficient rats) were examined by functional and radioligand binding studies. Enhanced PE-induced contractions and increased susceptibility to nifedipine in Mg-deficient rats were not observed in the presence of 10 microM H7. PE significantly decreased the KD value without changing Bmax in the binding of [3H]PN200-110 to de-endothelialized aortic strips. The KD value obtained in the Mg-deficient rats was significantly smaller than that in the controls. Nifedipine displaced the binding of [3H]PN200-110 concentration-dependently, and the pKi value in Mg-deficient rats was significantly larger than that in the controls. A combination of PE and H7 abolished this difference. These results indicate that the modulation of L-type Ca2+ channels via the stimulation of alpha 1-adrenoceptors may be involved in the enhancement of vasoconstriction and increased susceptibility to nifedipine in aortas isolated from Mg-deficient rats. The H7-sensitive mechanisms may play an important role in these phenomena.

Participation of alpha 1- and beta 1-adrenoceptors in norepinephrine-induced contraction and relaxation of isolated equine coronary artery in vitro

In coronary arterial rings isolated from horse, norepinephrine (NE)(10(-7) - 10(-5) M) induced concentration-dependent contractions which were not influenced by endothelial denudation. Prazosin (alpha 1-antagonist) inhibited the contraction, but yohimbine (alpha 2-antagonist) did not, and propranolol (beta-antagonist) enhanced the contraction. Pretreatment with phentolamine (10(-5) M) (alpha-antagonist) converted the contraction induced by NE to relaxation in coronary rings precontracted with ONO11113 (thromboxane A2 derivative). The relaxation was not influenced by removal of the endothelium, and was inhibited by propranolol and atenolol (beta 1-antagonist) but not by butoxamine (beta 2-antagonist). These results suggest that in equine coronary arteries, the contractile response to NE is mediated by stimulation of alpha 1-adrenoceptors on the smooth muscle, and that stimulation of beta 1-adrenoceptors on the smooth muscle modifies the contraction by inducing relaxation.

Endovascular treatment of acute thrombotic occlusion of the cervical internal carotid artery associated with embolic occlusion of the middle cerebral artery: case report

A 68-year-old man with acute, total thrombotic occlusion of the right cervical internal carotid artery, associated with embolic occlusion of the ipsilateral middle cerebral artery, was treated by the endovascular approach, i.e., intra-arterial fibrinolysis and balloon angioplasty. Endovascular treatment for a totally occluded internal carotid artery is indicated in the very early stage where there is no thrombus or a short thrombus that can be evacuated. Fibrinolysis of the associated embolus in the middle cerebral artery, if any, can be done in the same session, enabling an early restoration of the blood flow.