Yutaka Kitagawa

Nara Medical University, Kashihara, Nara, Japan

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Publications (8)20.03 Total impact

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    ABSTRACT: In consideration of clinical implications, it is often complained that short-term experimental diseased heart models do not mimic long-term diseased hearts that are often clinically encountered. The aim of the present study was (i) to compare the left ventricular function between rat cardiac hypertrophy models treated with isoproterenol for 3 days (Iso 3d) and 7 days (Iso 7d) by pressure-volume measurements with a catheter method, and (ii) to follow up the left ventricular function in the same model treated with Iso up to 16 weeks with a less-invasive echocardiography. An infusion of either Iso (1.2 mg x kg(-1) x day(-1) for 3 days-16 weeks) or vehicle (saline 24 microl x day(-1) for 3 days-16 weeks; Sa group) was performed by subcutaneously implanting an osmotic minipump. There were no significant differences in the systolic pressure-volume area at midrange left ventricular volume (PVA(mLVV): a mechanical work capability index) between Iso 3d and 7d groups, though PVA(mLVV) in both groups was significantly reduced from that in the Sa group. From echocardiography, the left ventricular function of the hypertrophy models at 3 days, 1 week, and 2 weeks was unchanged, but the model at a term longer than 4 weeks resulted in prolonged systolic failure. The results indicated that (i) no marked differences in the left ventricular mechanical work capability were found between the Iso 3d and 7d groups, and that (ii) only a 3-day Iso infusion induced the hypertrophy model similar in shape and function to that induced by a 2-week Iso infusion. We concluded that the 3-day model was sufficient.
    No preview · Article · Jul 2008 · The Journal of Physiological Sciences
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    ABSTRACT: The aim of the present study was performed to determine whether a novel histone deacetylase (HDAC) inhibitor, N-(2-aminophenyl)-4-{[benzyl(2-hydroxyethyl)amino]methyl} benzamide (K-183), prevents a reversible cardiac hypertrophy induced by isoproterenol and improves left ventricular (LV) dysfunction in rats. Either isoproterenol or vehicle was infused for 3 days by osmotic minipump. One hour prior to the implantation of isoproterenol, K-183 or trichostatin A (TSA) was injected twice a day for 3 days. We recorded continuous LV pressure-volume (P-V) loops of in situ hearts one hour after removal of the osmotic minipump. LV work capability (systolic P-V area at midrange LV volume: PVA(mLVV)) and hemodynamics were evaluated. K-183 per se induced neither cardiac hypertrophy nor collagen production. Although K-183 did not prevent the hypertrophy, where PVA(mLVV) remained decreased, K-183, differently from TSA, significantly attenuated the decrease of cardiac output and the increase of effective arterial elastance in the hypertrophied heart. These results indicate that the novel HDAC inhibitor K-183 has some beneficial effects on hemodynamics, although K-183 has no effects of anti-hypertrophic modalities.
    No preview · Article · Jul 2007 · Journal of Pharmacological Sciences
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    ABSTRACT: Although the cardiac protective and negative inotropic effects of nicorandil via opening the sarcolemmal or mitochondrial K(ATP) channel and NO-like action are well known, positive inotropic effects of nicorandil in normal hearts have not been reported. The aim of the current study was to investigate how nicorandil affects left ventricular (LV) function of in situ adult rat hearts through the entire cardiovascular system. We performed simultaneous and continuous measurements of LV pressure (P) by a catheter-tip micromanometer and LV volume (V) using a conductance catheter. We obtained steady-state LV P-V loops and intermittent curvilinear LV end-systolic pressure-volume relations (ESPVRs), LV end-systolic pressure (ESP(mLVV)), and systolic pressure-volume area (PVA(mLVV)) at midrange LVV (mLVV). We evaluated the effects of nicorandil on LV function by these mechanical indexes sensitively reflecting changes in LV contractility and work capability, preload (end-diastolic volume, EDV), and afterload (effective arterial elastance, Ea). Nicorandil (10 and 20 microg.kg(-1).min(-1)) (blood concentration: 0.53 +/- 0.14 and 1.48 +/- 0.21 microg/ml) largely shifted ESPVR upward and thus significantly increased ESP(0.06), PVA(0.06), stroke volume due to increase in EDV, and ejection fraction without significant changes in Ea and heart rate. In contrast, an NO donor, nitroglycerin (1 microg.kg(-1) . min(-1)), significantly decreased Ea but did not change ESP(0.06), PVA(0.06), and EDV. Furthermore, either a nonselective K(ATP) channel blocker, glybenclamide, or a mitochondrial K(ATP) channel blocker, 5-hydroxydecanoate, abolished these nicorandil-induced positive inotropic actions. These results suggest that nicorandil exhibited positive inotropic actions on LV function of in situ hearts in adult rats with resultant increased preload (EDV).
    No preview · Article · Feb 2005 · Journal of Anesthesia
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    ABSTRACT: Propofol is short-acting intravenous general anesthetics that reduces cardiovascular hemodynamics. The effects of propofol on intrinsic myocardial contractility, however, remain debatable. The aim of the current study was to test the hypothesis that inhibitory effects of propofol on left ventricular (LV) contractility and mechanical work capability of in situ ejecting rat hearts are attenuated after a brief regional ischemia and reperfusion. The authors obtained steady-state LV pressure-volume loops and intermittently obtained LV end-systolic pressure-volume relation and evaluated effects of propofol on LV function by end-systolic pressure (ESPmLVV), systolic pressure-volume area (PVAmLVV) at midrange LV volume (mLVV). Propofol (5.2 +/- 0.3 approximately 11.1 +/- 3.7 microg.ml) significantly decreased ESP0.08 to 78 +/- 12% approximately 64 +/- 13% of prepropofol and PVA0.08 to 76 +/- 13%approximately 63 +/- 16% of prepropofol in normal hearts, whereas propofol at a lower concentration (4.1 +/- 1.0 microg/ml) did not. Although brief ischemic-reperfusion per se did not affect LV function, propofol after that, even at a lower concentration (4.1 +/- 1.0 microg/ml), significantly decreased ESP0.08 to 70 +/- 27% of prepropofol and PVA0.08 to 68 +/- 33% of prepropofol. Pretreatment with a protein kinase C (PKC) inhibitor, bisindolylmaleimide reduced the propofol (4.1 +/- 1.0 microg/ml)-induced greater decreases in ESP0.08 and PVA0.08 after brief ischemic-reperfusion to 94 +/- 33% and 92 +/- 39% of prepropofol. In the propofol-infused hearts after brief ischemic-reperfusion, protein kinase C-epsilon translocation to the nucleus-myofibril fraction was found. In contrast to the study hypothesis, brief ischemic-reperfusion enhanced the inhibitory effects of propofol on LV systolic function; this enhancement is attributable to activation of protein kinase C.
    No preview · Article · Nov 2004 · Anesthesiology
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    Yutaka Kitagawa · Daisuke Yamashita · Haruo Ito · Miyako Takaki
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    ABSTRACT: The aim of the present study was to evaluate specifically left ventricular (LV) function in rat hearts as they transition from the normal to hypertrophic state and back to normal. Either isoproterenol (1.2 and 2.4 mg.kg(-1).day(-1) for 3 days; Iso group) or vehicle (saline 24 microl.day(-1) for 3 days; Sa group) was infused by subcutaneous implantation of an osmotic minipump. After verifying the development of cardiac hypertrophy, we recorded continuous LV pressure-volume (P-V) loops of in situ ejecting hypertrophied rat hearts. The curved LV end-systolic P-V relation (ESPVR) and systolic P-V area (PVA) were obtained from a series of LV P-V loops in the Sa and Iso groups 1 h or 2 days after the removal of the osmotic minipump. PVA at midrange LV volume (PVA(mLVV)) was taken as a good index for LV work capability (13, 15, 20, 21). However, in rat hearts during remodeling, whether PVA(mLVV) is a good index for LV work capability has not been determined yet. In the present study, in contrast to unchanged end-systolic pressure at midrange LV volume, PVA(mLVV) was significantly decreased by isoproterenol treatment relative to saline; however, these measurements were the same 2 days after pump removal. Simultaneous treatment with a beta(1)-blocker, metoprolol (24 mg.kg(-1).day(-1)), blocked the formation of cardiac hypertrophy and thus PVA(mLVV) did not decrease. The reversible changes in PVA(mLVV) reflect precisely the changes in LV work capability in isoproterenol-induced hypertrophied rat hearts mediated by beta(1)-receptors. These results indicate that the present approach may be an appropriate strategy for evaluating the effects of antihypertrophic and antifibrotic modalities.
    Full-text · Article · Aug 2004 · AJP Heart and Circulatory Physiology
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    ABSTRACT: Left ventricular (LV) myocardial slices were isolated from murine hearts (300 microm thick) and were stimulated at 1 Hz without external load. Mean myocardial slice O(2) consumption (MVo(2)) per minute (mMVo(2)) without stimulation was 0.97 +/- 0.14 ml O(2).min(-1).100 g LV(-1) and mean mMVo(2) with stimulation increased to 1.80 +/- 0.17 ml O(2).min(-1).100 g LV(-1) in normal Tyrode solution. Mean DeltamVo(2) (the mMVo(2) with stimulation - the mMVo(2) without stimulation) was 0.83 +/- 0.12 ml O(2).min(-1).100 g LV(-1). There were no differences between mean mMVo(2) with and without stimulation in Ca(2+)-free solution. The increases in extracellular Ca(2+) concentrations up to 14.4 mM did not affect the mMVo(2) without stimulation but significantly increased the mMVo(2) with stimulation up to 140% of control. The DeltamMVo(2) significantly increased up to 190% of the control in a dose-dependent manner. In contrast, the shortening did not increase in a dose-dependent manner. Cyclopiazonic acid (CPA; 30 microM) significantly reduced the DeltamMVo(2) to 0.27 +/- 0.06 ml O(2).min(-1).100 g LV(-1) (35% of control). The combination of 5 mM 2,3-butanedione monoxime (BDM) and 30 microM CPA did not further decrease DeltamMVo(2). Although BDM (3-5 mM) decreased the DeltamMVo(2) by 28-30% of control in a dose-independent manner, 3-5 mM BDM decreased shortening in a dose-dependent manner. Our results indicate that the DeltamMVo(2) of mouse LV slices during shortening under mechanically unloaded conditions consists of energy expenditure for total Ca(2+) handling during excitation-contraction coupling, basal metabolism, but no residual cross-bridge cycling.
    No preview · Article · Aug 2004 · AJP Heart and Circulatory Physiology
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    ABSTRACT: We have reported that the postextrasystolic (PES) potentiation of left ventricular (LV) contractility usually decays in alternans at heart rates above 80-100 beats/min in the canine excised, cross-circulated heart. We examined whether the PES contractility would also decay in alternans even in the canine in situ heart presumably more physiological than the excised heart. In anesthetized, ventilated, and open-chest mongrel dogs, we measured LV pressure and volume with a micromanometer and a conductance catheter cannulated into the LV and obtained LV end-systolic maximum elastance (E(max)) as the reasonably load-independent contractility index. We inserted an extrasystole followed by a compensatory pause into steady-state regular beats at heart rates above 90 beats/min and analyzed the PES decay pattern of E(max). We found that E(max) potentiated in the first PES beat decayed in alternans within 5-6 PES beats. This indicates that PES contractility also decays in alternans in the normal canine in situ heart.
    No preview · Article · Sep 2003 · The Japanese Journal of Physiology
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