PubMed Health⌕ Search

Biomedical subjects

K Takeuchi

Publications and source records attributed to K Takeuchi.

At least 145 records · Page 8Linked to original sources
PubMed2001

Adrenodoxin-cytochrome P450scc interaction as revealed by EPR spectroscopy: comparison with the putidaredoxin-cytochrome P450cam system.

The cholesterol side-chain cleavage reaction catalyzed by cytochrome P450scc comprises three consecutive monooxygenase reactions (22R-hydroxylation, 20S-hydroxylation, and C(20)-C(22) bond scission) that produces pregnenolone. The electron equivalents necessary for the oxygen activation are supplied from a 2Fe-2S type ferredoxin, adrenodoxin. We found that 1:1 stoichiometric binding of oxidized adrenodoxin to oxidized cytochrome P450scc complexed with cholesterol or 25-hydroxycholesterol caused shifts of the high-spin EPR signals of the heme moiety at 5 K. Such shifts were not observed for the low-spin EPR signals. Ligation of CO or NO to the reduced heme of cytochrome P450scc complexed with reduced adrenodoxin and various steroid substrates did not cause any change in the axial EPR spectrum of the reduced iron-sulfur center at 77 K. These results are in remarkable contrast to those obtained for the cytochrome P450cam-d-camphor-putidaredoxin ternary complex, suggesting that the mode of cross talk between adrenodoxin and cytochrome P450scc is very different from that in the Pseudomonas system. The difference may be primarily due to the location of the charged amino acid residues of the ferredoxins important for the interaction with the partner cytochrome P450.

Adrenal Cortex↗
PubMed2001

Multiethnic comparison of adolescent major depression based on the DSM-IV criteria in a U.S.-Japan study.

OBJECTIVES: To compare the prevalence rates of major depression based on the DSM-IVcriteria with data from a multiethnic sample of adolescents drawn from the same U.S.-Japan study and to investigate the relation of adolescent major depression to ethnicity. METHOD: Adolescents aged 12-15 years (N= 2,046; 539 Anglo-American, 636 African-American, 409 Mexican-American, and 462 Japanese adolescents) were studied in 1994 (response rates: 85.3% for U.S. students and 95.5% for Japanese students). The DSM Scale for Depression, a self-administered checklist developed from the Diagnostic Interview Schedule for Children questions on major depression, was used to estimate the prevalence of DSM-IV major depression. RESULTS: The overall prevalence rates of major depression without/with impairment were 9.6% and 4.3% for Anglo-American, 13.4% and 6.1 % for African-American, 16.9% and 9.0% for Mexican-American, and 5.6% and 1.3% for Japanese adolescents. The significant association between adolescent major depression and ethnicity disappeared after sociodemographic adjustments. Only fathers' educational attainment and family financial status remained significant (odds ratios: 3.28-5.30 for grade school for fathers and 2.62-2.78 for being worse off economically). CONCLUSION: These findings imply ethnicity does not have a significant impact on the risk of adolescent major depression after sociodemographic adjustments.

Adolescent↗
PubMed2001

Clinical characteristics of acute hemorrhagic rectal ulcer.

BACKGROUND: Acute hemorrhagic rectal ulcer (AHRU) occurs suddenly with painless, massive, fresh rectal bleeding in elderly, bed-ridden patients who have a serious primary disease. There have been several reports on AHRU in Japan, but in Western countries, there have been none. We examined the clinical characteristics of four cases, and we report on AHRU in Western countries. STUDY: The medical records and endoscopic findings in four patients with AHRU seen during a 3-year period were reviewed. The diagnosis of AHRU was established by clinical symptoms, endoscopic examination, and other methods. RESULTS: All of the patients were elderly and bed-ridden and all had sudden onset of massive, fresh rectal bleeding without pain. Sigmoidoscopic examination of all patients showed a shallow or irregular bleeding ulcer in the lower rectum. In three cases, the clinical course was uneventful. In the other case, massive, fresh rectal bleeding recurred but transanal ligation was effective. CONCLUSIONS: When painless, massive, fresh rectal bleeding occurs in elderly and bed-ridden patients, it is important to carefully examine the lower rectum, as there is a strong possibility of AHRU.

Aged↗
PubMed2001

Effects of SK&F 96365 and mefenamic acid on Ca2+ influx in stimulated endothelial cells and on endothelium-derived hyperpolarizing factor-mediated arterial hyperpolarization and relaxation.

This study was undertaken to assess how Ca2+ influx into endothelial cells via Ca2+-permeable nonselective cation channels (NSCCs) is important in vascular responses mediated by endothelium-derived hyperpolarizing factor (EDHF). In cultured porcine aortic endothelial cells, the sustained increases in the intracellular Ca2+ concentration ([Ca2+]i) elicited by bradykinin and cyclopiazonic acid, which were strongly dependent on the presence of extracellular Ca2+, were suppressed by the NSCC blockers, SK&F 96365 and mefenamic acid. In porcine coronary artery with intact endothelium, bradykinin elicited a rapid fall in the membrane potential, followed by sustained hyperpolarization with a slow decay. In the presence of SK&F 96365 or mefenamic acid, the peak amplitude was severely reduced and the decay phase of hyperpolarization to bradykinin was greatly accelerated, which was apparently similar to the response obtained in Ca2+-free medium. Cyclopiazonic acid caused sustained hyperpolarization in an extracellular Ca2+-dependent manner, an effect which was markedly diminished by SK&F 96365 and mefenamic acid. In rings of coronary artery precontracted with U46619, bradykinin and cyclopiazonic acid produced endothelium-dependent relaxations even in the presence of N(G)-nitro-L-arginine and indomethacin. SK&F 96365 and mefenamic acid significantly attenuated the relaxant responses. These results indicate that the increase in [Ca2+]i of endothelial cells due to Ca2+ entry via NSCCs plays a crucial role in the maintenance of the EDHF-mediated vascular responses.

Animals↗
PubMed2001

Insulin inhibits coronary endothelial cell calcium entry and coronary artery relaxation.

Hyperinsulinemia is closely related to coronary artery disease. Endothelial cells are important for the control of vascular tone, and dysfunction of endothelial cells has been implicated in coronary artery disease. The direct effects of insulin on coronary endothelial cells are nonetheless unknown. In this study, the acute effects of high-dose insulin were investigated on agonist-induced intracellular Ca(2+) concentration ([Ca(2+)](i)) in porcine coronary endothelial cells and coronary relaxation. Bradykinin (10 n M ) and cyclopiazonic acid (100 microM), an inhibitor of the endoplasmic reticulum Ca(2+)-ATPase, provoked large increases in [Ca(2+)](i) in coronary endothelial cells. This increase was dose-dependently inhibited by a 10-min preincubation with high doses of insulin (10, 30, 100 mU/ml). Under Ca(2+)-free conditions, bradykinin and cyclopiazonic acid provoked transient, small increases in [Ca(2+)](i). These increases were not affected by pretreatment with insulin (100 mU/ml). Bradykinin (1, 10, 100, 1,000 n M ) and cyclopiazonic acid (10 microM) significantly relaxed porcine coronary artery rings precontracted with histamine (1 microM). The vasodilator effects of bradykinin and cyclopiazonic acid were dose-dependently inhibited by insulin. These acute effects were not observed at physiologic concentrations. Our data indicate that high-dose insulin inhibits agonist-induced Ca(2+) response in coronary endothelial cells and attenuates agonist-induced coronary vasodilatation. The study suggests that hyperinsulinemia might be associated with coronary artery disease via derangement of endothelial Ca(2+)-dependent functions.

Animals↗
PubMed2001

Paramyxovirus accessory proteins as interferon antagonists.

A new role of the Paramyxovirus accessory proteins has been uncovered. The P gene of the subfamily Paramyxovirinae encodes accessory proteins including the V and/or C protein by means of pseudotemplated nucleotide addition (RNA editing) or by overlapping open reading frame. The Respirovirus (Sendai virus and human parainfluenza virus (hPIV)3) and Rubulavirus (simian virus (SV)5, SV41, mumps virus and hPIV2) circumvent the interferon (IFN) response by inhibiting IFN signaling. The responsible genes were mapped to the C gene for SeV and the V gene for rubulaviruses. On the other hand, wild type measles viruses isolated from clinical specimens suppress production of IFN, although responsible viral factors remain to be identified. Both human and bovine respiratory syncytial viruses (RSVs) counteract the antiviral effect of IFN with inhibiting neither IFN signaling nor IFN production. Bovine RSV NS1 and NS2 proteins cooperatively antagonize the antiviral effect of IFN. Studies on the molecular mechanism by which viruses circumvent the host IFN response will not only illustrate co-evolution of virus strategies of immune evasion but also provide basic information useful for engineering novel antiviral drugs as well as recombinant live vaccine.

Base Sequence↗
PubMed2001

Establishment of cell lines with high- and low-metastatic potential from PC-14 human lung adenocarcinoma.

This article reports the establishment of variant cell lines with high and low metastatic potential by repeated selection and the dilution plating technique. Five clones with high metastatic potential, Lu-2, Lu-7, Lu-4, Lu-1 and Lu-5, and four clones with low metastatic potential, 3S, 7S, 8S and 13S, were established from PC-14 human lung adenocarcinoma. The high-metastatic cell lines produced enhanced lung metastases, but the low-metastatic cell lines did not produce lung metastasis by injection into the tail vein of 5-week-old BALB / c nude mice. The high-metastatic cell lines produced enhanced tumors on both visceral and parietal pleurae, and enhanced metastases to the mediastinum and contralateral pleural cavity. The low-metastatic cell lines produced reduced tumors on both visceral and parietal pleurae and reduced metastases to the mediastinum and contralateral pleural cavity after injection into the left preceral cavity of the nude mice. When the nine variant cell lines and original PC-14 cells were embedded in collagen gels, the PC-14 cells and the low-metastatic cell lines gave rise to colonies with a dendritic morphology, and cells were tightly associated. The high-metastatic cell lines were more loosely associated and scattered into three-dimensional colonies. These nine cloned cell lines originated from heterogeneous populations of the parental PC-14 cells should be useful tools for studying the process of metastasis of lung cancer.

Adenocarcinoma↗
PubMed2001

Prediction of contractile reserve by cyclic variation of integrated backscatter of the myocardium in patients with chronic left ventricular dysfunction.

OBJECTIVE: To clarify whether assessment of the acoustic properties of the myocardium at rest can predict contractile reserve in patients with chronic left ventricular dysfunction. METHODS: 23 patients (mean (SD) age 63 (12) years) with chronic left ventricular dysfunction were studied. The magnitude of cardiac cycle dependent variation of integrated backscatter (CVIB) of the myocardium was measured at rest in the basal and mid segment of the septum and posterior wall of the left ventricle, using a real time two dimensional integrated backscatter imaging system. The results were compared with the percentage wall thickening and the wall motion at rest and during low dose dobutamine infusion. The wall motion was graded as normal, hypokinetic, or akinetic and contractile reserve was considered present when an akinetic or hypokinetic segment improved during dobutamine infusion. RESULTS: The CVIB at rest correlated with per cent wall thickening at rest and during dobutamine infusion (at rest, r = 0.61, p < 0.0001, during dobutamine, r = 0.76, p < 0.0001). Of the 76 segments examined, 27 showed contractile reserve. The mean CVIB at rest was significantly greater in segments with contractile reserve than in those without (p < 0.0001). CVIB above 3 dB at rest predicted segments with contractile reserve with a sensitivity and specificity of 81% and 60%, respectively (p < 0.0001). CONCLUSIONS: CVIB reflected not only myocardial contractility but also the functional capacity of the myocardium. It predicted segmental contractile reserve in patients with chronic left ventricular dysfunction.

Adult↗
PubMed2001

Detection of malignant tumors: whole-body PET with fluorine 18 alpha-methyl tyrosine versus FDG--preliminary study.

PURPOSE: To compare the diagnostic potential of whole-body positron emission tomography (PET) with fluorine 18 alpha-methyl tyrosine (FMT) with that of whole-body PET with 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG). MATERIALS AND METHODS: Nineteen patients with or suspected of having malignant tumors and five healthy volunteers underwent whole-body PET with FMT and FDG. RESULTS: In comparison with FDG uptake, FMT uptake was significantly less in the brain, heart, lung, liver, and spine. On a lesion-by-lesion basis, the sensitivity of whole-body FMT PET for depicting malignant tumors was inferior to that of whole-body FDG PET, but this difference was not statistically significant (74% [26 of 35 lesions] vs 91% [32 of 35 lesions], P >.05). The positive predictive value of FMT PET was superior to that of FDG PET (87% [26 of 30 lesions] vs 63% [32 of 51 lesions], P <.001). The difference in uptake between benign and malignant lesions was significant with FMT PET (mean +/- SD, 1.64 +/- 0.96 vs 0.79 +/- 0.23; P <.001) but not with FDG PET (5.02 +/- 3.56 vs 4.02 +/- 2.90, P >.05). CONCLUSION: Whole-body FMT PET is clinically useful in the diagnosis of malignant tumors and may be effective in the depiction of primary and metastatic lesions in the cardiac region or in the brain.

Adult↗
PubMed2001

Less damaging effect of whisky in rat stomachs in comparison with pure ethanol. Role of ellagic acid, the nonalcoholic component.

BACKGROUND/AIM: Ellagic acid (EA), one of the polyphenols that are abundantly contained in whisky as a nonalcoholic component, has antioxidant and anti-inflammatory activities. In the present study, we compared the action of whisky and pure ethanol on the rat gastric mucosa, and examined the role of EA in the less-damaging effect of whisky in the stomach. METHODS: Under urethane anesthesia, a rat stomach was mounted in an ex vivo chamber, perfused with saline, and the transmucosal potential difference (PD) was measured before and after exposure to whisky (Yamazaki, Suntory) and ethanol (43%). In a separate study, the animals were given whisky or ethanol (1 ml, 43%) p.o. under unanesthetized conditions, killed 1 h later, and the gastric mucosa was examined for hemorrhagic lesions. RESULTS: Both whisky and ethanol caused a PD reduction, resulting in damage in the stomach, but these responses were less marked in the case of whisky. Although the reduced PD recovered gradually after removal of ethanol, this process was significantly expedited by co-application of EA (80 microg/ml), the recovery rate being much the same as that observed after exposure to whisky. The less-damaging effect of whisky was confirmed in unanesthetized rats after p.o. administration of these agents. In addition, EA (1-30 mg/kg), administered p.o. together with absolute ethanol (99.9%), reduced the severity of gastric lesions induced by ethanol, in a dose-dependent manner, and the effect at 30 mg/kg was equivalent to that obtained by the whisky component containing several low- and high-molecular-weight polyphenols. EA had a scavenging action against both oxygen and hydroxyl radicals in vitro, the effect being equivalent to that of catechol or alpha-tocopherol. CONCLUSION: These results suggest that whisky is less irritating to the gastric mucosa, as compared with pure ethanol, and this property of whisky may be explained by EA, one of polyphenols contained in whisky, and its radical scavenging action.

Alcoholic Beverages↗
PubMed2001

Prostaglandin E inhibits indomethacin-induced gastric lesions through EP-1 receptors.

BACKGROUNDS AND AIMS: We examined the effect of various prostaglandin E (PGE) analogs specific to EP receptor subtypes on indomethacin-induced gastric lesions in rats and investigated which EP receptor subtype is involved in the protective action of PGE(2) using EP-receptor knockout mice. METHODS: Gastric lesions were induced by subcutaneous administration of indomethacin (35 mg/kg). Gastric motility was measured using a balloon method, while neutrophil chemotaxis determined using a Boyden chamber. RESULTS: Indomethacin-induced gastric lesions were significantly prevented by PGE(2) as well as atropine, and the former effect was mimicked by sulprostone (EP(1)/EP(3)) and 17-phenyl PGE(2) (EP(1)) and antagonized by an EP(1) antagonist, ONO-AE-829. Neither butaprost (EP(2)), ONO-NT-012 (EP(3)) nor 11-deoxy PGE(1) (EP(3)/EP(4)) showed any protection on the lesions. Indomethacin caused a marked increase in gastric motility; the response preceded the onset of lesions and was inhibited by atropine as well as PGE derivatives acting as EP(1) receptors. Neutrophil chemotaxis was inhibited by PGE(2), butaprost and slightly by 11-deoxy PGE(1), but not by either 17-phenyl PGE(2), ONO-NT-012 or atropine. In addition, indomethacin caused damage similarly in both wild-type and knockout mice lacking EP(1) or EP(3) receptors, yet the protective action of PGE(2) was observed in wild-type and EP(3) receptor knockout mice but totally disappeared in mice lacking EP(1) receptors. CONCLUSION: PGE(2) inhibits indomethacin-induced gastric lesions, through EP(1) receptors, and this effect may be functionally associated with inhibition of gastric motility but not of neutrophil activation/migration.

Animals↗
PubMed2001

Delayed healing of gastric ulcers in adjuvant arthritis rats: role of acid secretion and basic fibroblast growth factor.

BACKGROUND/AIM: We examined the healing process of chronic gastric ulcers in adjuvant-induced arthritic rats and investigated the mechanism for delayed ulcer healing in arthritic rats, in relation to acid secretion and basic fibroblast growth factor (bFGF). METHODS: Arthritis was induced in male dark Agouti rats by a single injection of Freund's complete adjuvant (FCA), while gastric ulcers were induced by thermal cauterization (70 degrees C for 30 s) 7 days after FCA injection. RESULTS: Injection of FCA induced severe arthritis in all animals with a marked acid hypersecretion. The healing of gastric ulcers was significantly delayed in arthritic rats as compared with normal rats. Daily administration of indomethacin delayed ulcer healing in both normal and arthritic rats, but this effect was more pronounced in the latter. In contrast, the healing of gastric ulcers was significantly promoted in both normal and arthritic rats by omeprazole at a dose that inhibited acid secretion completely. The delayed healing of gastric ulcers was not influenced by twice daily administration of N(G)-nitro-L-arginine methyl ester, aminoguanidine or FR167653 (IL-1/TNF-alpha synthesis inhibitor), but was significantly accelerated by CS-23 (recombinant human bFGF) in a dose-dependent manner, without effect on the acid secretion. The expression of bFGF was markedly increased after ulceration, but this response was decreased in arthritic rats. CONCLUSION: The healing of gastric ulcers was delayed in arthritic rats, and this mechanism may be partly attributable to both acid hypersecretion and less expression of bFGF.

Animals↗
PubMed2001

Myosin light chain kinase regulates capacitative ca(2+) entry in human monocytes/macrophages.

Monocytes/macrophages are present in all stages of atherosclerosis. Although many of their activities depend to various extents on changes in intracellular Ca(2+) concentration ([Ca(2+)](i)), mechanisms regulating [Ca(2+)](i) in these cells remain unclear. We aimed to explore the role of myosin light chain kinase (MLCK) in Ca(2+) signaling in freshly isolated human monocytes/macrophages. Large capacitative Ca(2+) entry (CCE) was observed under fura 2 fluoroscopy in human monocytes/macrophages treated with thapsigargin and cyclopiazonic acid. ML-9 and wortmannin, 2 structurally different inhibitors of MLCK, dose-dependently (1 to 100 micromol/L) prevented CCE and completely did so at 100 micromol/L, whereas inhibitors of tyrosine kinase and protein kinase C had only partial effects. Western blotting showed that thapsigargin significantly caused myosin light chain phosphorylation, which was almost completely blocked by ML-9 (100 micromol/L) and wortmannin (100 micromol/L). ML-9 also dose-dependently (1 to 100 micromol/L) inhibited this phosphorylation, which was well correlated with its inhibition of CCE. Transfection with MLCK antisense completely prevented CCE in response to thapsigargin and cyclopiazonic acid, whereas MLCK sense had no effect. These data strongly indicate that MLCK regulates CCE in human monocytes/macrophages. The study suggests a possible involvement of MLCK in many Ca(2+)-dependent activities of monocytes/macrophages.

Androstadienes↗
PubMed2001

Transcriptional suppression of type 1 angiotensin II receptor gene expression by peroxisome proliferator-activated receptor-gamma in vascular smooth muscle cells.

Angiotensin (A) II plays a critical role in vascular remodeling, and its action is mediated by type 1 AII receptor (AT1R). Recently, 15-deoxy-(Delta)(12,14)-prostaglandin J(2) and thiazolidinediones have been shown to be ligands for peroxisome proliferator-activated receptor (PPAR)-gamma and activate PPAR-gamma. In the present work, we have studied the effect of PPAR-gamma on AT1R expression in rat vascular smooth muscle cells (VSMCs). We observed that: 1) endogenous AT1R expression was significantly decreased by PPAR-gamma ligands both at messenger RNA and protein levels, whereas AT1R messenger RNA stability was not affected; 2) AII-induced increase of (3)H-thymidine incorporation into VSMCs was inhibited by PPAR-gamma ligands; 3) rat AT1R gene promoter activity was significantly suppressed by PPAR-gamma ligands, and PPAR-gamma overexpression further suppressed the promoter activity; 4) transcriptional analyses using AT1R gene promoter mutants revealed that a GC-box-related sequence within the -58/-34 region of the AT1R gene promoter was responsible for the suppression; 5) Sp1 overexpression stimulated AT1R gene transcription via the GC-box-related sequence, which was inhibited by additional PPAR-gamma overexpression; 6) electrophoretic mobility shift assay suggested that Sp1 could bind to the GC-box-related sequence whereas PPAR-gamma could not; 7) antibody supershift experiments using VSMC nuclear extracts revealed that protein-DNA complexes formed on the GC-box-related sequence, which were decreased by PPAR-gamma coincubation, were mostly composed of Sp1; and 8) glutathione S-transferase pull-down assay revealed a direct interaction between PPAR-gamma and Sp1. Taken together, it is suggested that activated PPAR-gamma suppresses AT1R gene at a transcriptional level by inhibiting Sp1 via a protein-protein interaction. PPAR-gamma ligands, thus, may inhibit AII-induced cell growth and hypertrophy in VSMCs by AT1R expression suppression and possibly be beneficial for treatment of diabetic patients with hypertension and atherosclerosis.

Angiotensin II↗
PubMed2001

Application of Eudragit P-4135F for the delivery of ellagic acid to the rat lower small intestine.

Based on the assumption that the delivery of ellagic acid to its site of action would show an antiinflammatory activity in inflammatory bowel disease (IBD), we have prepared microspheres using a new pH-sensitive polymer, Eudragit P-4135F (P-4135F), to deliver ellagic acid to the lower small intestine in rats. The microspheres were spherical in shape and the mean diameters were approximately 100-150 microm. The amount of ellagic acid released from the microspheres decreased by increasing the formulated amount of P-4135F. The release characteristics of ellagic acid were pH-dependent. By considering the factors loading efficiency and microsphere particle size distribution, ellagic acid-2 microspheres (P-4135F/ellagic acid = 1.65) were selected for further investigation. In a dissolution study, more than 95% ellagic acid was released within 0.5 h in pH 7.4 and 8.0 buffers. The release percent of ellagic acid was less than 40% in pH 6.8 and 7.0 and was less than 10% in pH 5.6 and 5.9. To observe the dissolution sites of the microspheres in the rat small intestine fluorescein was formulated in the microspheres as a tracer drug along with ellagic acid (50 mg kg(-1)). After intraduodenal administration of fluorescein-labelled microspheres to rats, the plasma fluorescein level started to increase at 0.5 h, by which time the microspheres had reached the middle part of the ileum. Microspheres started to dissolve within 1.0 h and the peak plasma fluorescein concentration was observed at 3.0 h, when the majority of the administered microspheres were dissolved in the terminal ileum. These results suggested that P-4135F microspheres could deliver ellagic acid to the lower part of the small intestine, and that the released ellagic acid would be distributed into the caecum and the ascending colon.

Administration, Oral↗
PubMed2001

Effects of dermatan and dextran sulfates on arginine amidase activity released from isolated rabbit arteries.

We examined the levels of arginine amidase secreted from isolated rabbit arteries treated with dermatan and dextran sulfates, and the relation between the secretion of arginine amidase activity and the concentration of dermatan sulfate added to these arteries. The results showed that while dextran sulfate tended to accelerate the release of arginine amidase activity from the isolated rabbit ear artery, the induction was not significant. There was a significant increase in the level of arginine amidase released from the lower portion of isolated rabbit aorta (p<0.05), but no significant change in the upper portion of the aorta. In contrast, the addition of dermatan sulfate significantly increased the level of arginine amidase activity released from the isolated rabbit ear artery and the upper and lower portions of the aorta (p<0.05). Linear dose-response relationships were observed between the level of arginine amidase activity released from the isolated rabbit ear artery and aorta and the concentration of dermatan sulfate added.

Animals↗
PubMed2001

Improving glucose metabolism and/or sarcoplasmic reticulum Ca2+-ATPase function is warranted for immature pressure overload hypertrophied myocardium.

The cellular mechanisms of abnormal calcium regulation and excitation-contraction coupling in relation to glucose metabolism in the hypertrophied heart are not well understood. The present study evaluated the myocardial mechanics of 6-7-week-old pressure overload hypertrophied rabbit hearts in response to dobutamine by (1) serial echocardiograms in vivo and (2) isolated Langendorff perfusion. Cytosolic Ca2+([Ca2+]i) and sarcoplasmic reticulum Ca2+-ATPase (SERCA2) expression were measured by fluorescence spectroscopy and Western immunoblotting, respectively. The effect of glycolytic inhibition by 2-deoxy-D-glucose +/- pyruvate was also evaluated. Both systolic and diastolic [Ca2+]i tended to be higher and diastolic calcium removal (tauCa) significantly slower in the hypertrophied heart. The myocardial response to dobutamine was blunted and dobutamine insignificantly improved tauCa. The SERCA2 protein level was higher in early hypertrophy, but was significantly reduced by 6 weeks of age, with progressive contractile failure. Inhibition of glycolysis or SERCA2 caused an increase in [Ca2+]i as well as a slower tauCa. Pyruvate completely preserved myocardial function and [Ca2+]i handling during glycolytic inhibition. It was concluded that in this model of advanced pressure overload hypertrophy, contractile failure and inotrope insensitivity are associated with increased [Ca2+]i, slower tauCa and reduced sensitivity of the contractile proteins to Ca2+. These changes occur in association with downregulation of the SERCA2, probably caused by impaired glucose metabolism.

Animals↗