Suguru Matsuoka

Endothelium-derived hyperpolarizing factor activates Ca2+-activated K+ channels in porcine coronary artery smooth muscle cells.

Although endothelium-derived hyperpolarizing factor (EDHF) activity has been demonstrated in arteries from various species, EDHF has not been chemically identified, nor its mechanism of action characterized. To elucidate this mechanism, we tested the effect of EDHF on large-conductance Ca2+-activated K+ (K(Ca)) channels in porcine coronary artery smooth muscle cells. By using a patch-clamp technique, single-channel currents were recorded in cultured smooth muscle cells; the organ bath also contained a strip of porcine coronary with endothelium, which served as the source of endothelium-derived relaxing factor(s) including EDHF. Exposure of endothelium to 10(-6) M bradykinin activated K(Ca) channels in cultured smooth muscle cells in cell-attached patches. When the experiment was performed in the presence of 10 microM indomethacin and 30 microM N(G)-nitro-L-arginine (L-NNA), which block the generation of prostaglandin I2 (PGI2) and NO, respectively, K(Ca) channel activity was stimulated by bradykinin, indicating the direct involvement of EDHF in K(Ca) channel stimulation. Neither 10 microM methylene blue nor 25 microM Rp-cAMPS inhibited bradykinin-induced K(Ca) channel activity. In inside-out patches, the addition of bradykinin to the solution was without effect on K(Ca) channel activation. However, in the presence of 0.5 mM guanosine triphosphate (GTP) and 1.0 mM adenosine triphosphate (ATP) in the bath solution, K(Ca) channels was activated by bradykinin. In outside-out patches, the addition of bradykinin also increased K(Ca) channel activity, when GTP and ATP were added to the pipette solution. The addition of GDP-beta-S (100 microM) in the cytosolic solution completely blocked the activation K(Ca) channels induced by bradykinin in inside-out and outside-out patches. Pretreatment with 30 microM quinacrine, a phospholipase A2 inhibitor, or 3 microM 17-octadecynoic acid (17-ODYA), a cytochrome P450 inhibitor, in addition to indomethacin and L-NNA, abolished bradykinin-stimulated K(Ca) channel activity in cell-attached patches. Both 14,15-epoxyeicosatrienoic acid (EET) and 11,12-EET increased the open probabilities of K(Ca) channels in cell-attached patches. These results suggest that EDHF, released from endothelial cells in response to bradykinin, hyperpolarizes smooth muscle cells by opening K(Ca) channels. Furthermore, our data suggest that EDHF is an endothelium-derived cytochrome P450 metabolite of arachidonic acid. The effect of EDHF on K(Ca) channels is not associated with an increase of cAMP and cGMP. The activation of K(Ca) channels appears to be due to the activation of GTP-binding protein.

Prevalence of specific allergic diseases in school children as related to parental atopy

Abstract Background: Our objective was to investigate the influence of parental allergy on the manifestations and course of allergic disease in children.

The effect of glutamate on hypoxic newborn rabbit heart

Effects of glutamate on myocardial mechanical function and energy metabolism during 120 min of hypoxia and subsequent reoxygenation were studied in the isolated arterially perfused newborn and adult rabbit hearts. The muscle was perfused with a Krebs-Henseleit (KH) solution or KH solution which contained 1 mM glutamate. Glutamate attenuated the effects of hypoxia on mechanical function and tissue ATP concentration, and enhanced the recovery of mechanical function and tissue ATP during reoxygenation. During hypoxia, glutamate increased tissue succinate and GTP with no change in total lactate and pyruvate production. Trace studies using 14C-glutamate and the tissue homogenate showed that hypoxia increased tissue succinate and inhibited TCA cycle. Additional glutamate produced more CO2 and TCA intermediates in both oxygenated and hypoxic mediums. These data indicate that glutamate increased the rate of ATP production in the hypoxic and reoxygenated heart. This study shows that the improvement of mechanical function and ATP formation in the hypoxic myocardium by glutamate was due to an increase in both oxidative phosphorylation and substrate level phosphorylation. The effect of glutamate on the ATP and GTP production in the newborn heart was not different from the adult.

Inotropic effects of prostaglandin D2 and E1 on the newborn rabbit heart.

ABSTRACT: This study determines the inotropic effects of prostaglandin D2 (PGD2) and prostaglandin E1 (PGE1) in the isolated, arterial perfused newborn (NB) and adult (A) rabbit heart.Significant positive inotropism of PGD2 was observed at all concentrations studied (1 × 10-17 to 1 × 10-7 M) in the two age groups; the effect in the NB was significantly greater (p < 0.05) than that in the A at PGD2 concentrations higher than 1 × 10-17 M. Significant positive inotropism of PGE1 was observed at PGE1 concentrations higher than 1 × 10-8 M in the NB, and only at 1 × 10-6 M in the A.In the NB, the relaxation parameters [1/2ART and the ratio of +dT/dt (max) to -dT/dt (max)] decreased to 80% of control after PGE1 infusion, but not after PGD2 infusion. In contrast, relaxation parameters in the A were not different from control.Propranolol (1 × 10-6 M) did not alter the positive inotropic action of PGD2 and PGE1 in the NB. These data indicate that: 1) the positive inotropic effects of PGD2 and PGE1 in NB are greater than that in the A, 2) PGE1 and not PGD2, enhances myocardial relaxation only in the NB,3) the contractile effects of PGD2 and PGE1 are not mediated by β-receptors.

Myocardial excitation-contraction coupling in the fetus of alloxan-diabetic rabbit.

ABSTRACT: This study was conducted to investigate myocardial excitation-contraction coupling in the fetus of the diabetic rabbit (FDM). On day 14 of gestation, diabetes was induced in pregnant rabbits by alloxan injection. On day 28 of gestation, mechanical function of the fetal myocardium was determined in the isolated arterially perfused heart preparation. At 1.5 mM [Ca2+]o (control), the force of myocardial contraction in FDM was not significantly dfferent from that in the control fetus. At higher [Ca2+]o, developed tension and maximal rate of tension development [+dT/dt (max)] in FDM were significantly greater than in the control fetus. High [Ca2+]o caused significant increases in resting tension and half-relaxation time (toxic effects) in the control fetus, but not in FDM. Perfusion with lanthanum (known to displace sarcolemma-bound Ca2+ and block sarcolemmal Na-Ca exchange) decreased developed tension and +dT/dt (max) and increased resting tension and these effects in FDM were significantly less than in the control fetus. Perfusion with manganese (known to displace Ca2+ from intracellular sites) also decreased developed tension and +dT/dt (max) and increased resting tension, and these effects were similar in the two groups. The myofibrillar ATPase activities at various calcium concentrations were not different between the two groups. The rates of Ca2+ uptake by mitochondria and sarcoplasmic reticulum were similar in the two groups. These data suggest that in FDM the inotropic effect of Ca2+ is greater and the toxic effect of Ca2+ is less than in the control fetus. This difference may be due, at least in part, to a sarcolemmal alteration induced by the maternal diabetes.

Effects of interventricular shunt on indices of left ventricular function.

ABSTRACT. The accuracies of indices of left ventricle function were examined in an open-chest model in dogs with and without a ventricular septal defect, in which the ventricular shunt was opened and reclosed by a specially designed flowmeter probe with a cap. The systolic time interval, the maximal rate of pressure development in the left ventricle (+LV dP/dt), +LV dP/dt corrected for the isometric pressure (+LV dP/dt /Pd), and the time to +LV dP/dt (t-dP/dt) were determined by recording the aortic flow, ventricular shunt flow, aortic pressure, pulmonary arterial pressure, and left ventricular pressure. The isometric contraction time, the preejectional period, and the ejection time shortened with decrease of the mean aortic pressure and aortic flow, and the mean pulmonary arterial pressure increased after opening the ventricular shunt. When the pulse was varied by atrial pacing, the systolic time interval was affected in dogs both with and without a ventricular septal defect, but “isometric contraction time” was not affected in animals with a ventricular septal defect. Dopamine and methoxamine were used to evaluate the effects of the inotropic state and afterload on these indices. The extents of the changes in the systolic time interval and +LV dP/dt were different in animals with and without a ventricular septal defect, but the changes in preejectional period/ejection time, +LV dP/dt/Pd and t-dP/dt were similar in the two conditions. These results suggest that the systolic time interval and the indices of left ventricular pressure are useful in assessment of cardiac function only in certain conditions.

Excursion of The Diaphragm in Duchenne Muscular Dystrophy with A Chest Respirator.

5例のDuchenne型筋ジストロフィー患者において, 体外式人工呼吸器使用時の横隔膜呼吸運動を検討した。呼気相, 吸気相の横隔膜の動きを胸部X線写真により全例で, うち2例では透視により確認した。また睡眠時パルスオキシメータにて低酸素血症が認められた2例では睡眠時の横隔膜呼吸運動を胸部X線写真で確認した。いずれの症例においても横隔膜呼吸運動は非常に弱かった。さらに睡眠時には酸素飽和度の低下した時点で, ほとんど横隔膜の動きが認められなかった。透視を行った2例中1例では横偏膜は吸気に頭側へ移動し, その後足方向へ, また他の1例では一度動きが停止し2段階移動になることがわかった。Duchenne型筋ジストロフィーのように筋力低下が進行性に悪化していく疾患では体外式人工呼吸器の有効性に限界があり, その実施中は定期的に, 特に睡眠時の呼吸機能評価を行わなくてはならない。

EFFECT OF HYPOXIA ON MITOCHONDRIAL ELECTRON TRANSPORT COMPLEXES AND ADENINE NUCLEOTIDES IN THE NEWBORN HEART

Effect of 60 min hypoxia (N2) and subsequent 40 min reoxygenation (re-02) on mitochondrial state 3 respiration (QO2), electron transport complexes (ETC), adenine nucleotides (AdN= ATP+ADP+AMP) and adenine nucleotide translocase (AdNT) activity were studied in isolated, arterially perfused newborn (NB) and adult (A) rabbit hearts. In the oxygenated muscle (control) QO2, AdNT and ATP were significantly (P<0.05) greater in NB than in A. After N2, QO2 and AdNT decreased significantly (P<0.01) in both age groups, and the values of Q02, AdN, and AdNT in the NB were significantly greater (P<0.05) than in A. N2 depressed ETC I in the A but not in the NB. After re-02, QO2 and AdN returned to control values in NB (96 ± 10% of control) but not in A (56 ± 3%), and the recovery of AdNT in NB (70 ± 2%) was significantly greater than in A (39 ± 5%). There was good correlation between QO2 and AdN as well as AdNT in both age groups. Conclusion: 1) the effect of N2 and re-02 on Q02, AdN, AdNT and ETC in NB is less than in A, 2) AdN is important in maintaining mitochondrial function.