• Title/Summary/Keyword: 수축력

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The Effects of Metabolic Substrates on Contractility of Isolated Rat Atria Depressed with Bupivacaine (Bupivacaine에 의해 억제된 심근수축력에 대한 대사기질의 영향)

  • Park, Seung-Joon;Chang, Joo-Ho;Jung, Jee-Chang;Ko, Kye-Chang
    • The Korean Journal of Pharmacology
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    • v.28 no.1
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    • pp.41-48
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    • 1992
  • A concentration of 0.01 mM bupivacaine was necessary to maintain approximately 50% depression of contractility of rat atria suspended in a modified Krebs-Ringer bicarbonate glucose medium, pH 7.4 at $30^{\circ}C$. Sodium pyruvate, sodium acetate, and fructose partially restored the contractility of the bupivacaine-depressed atria. However, 20 mM glucose had no effect on the bupivacaine-depressed atria, although this concentration of glucose markedly increased the contractility of normal atria not to be exposed to bupivacaine. Contractility of normal atria was not significantly influenced by sodium pyruvate, sodium acetate, and fructose. The results suggested that at least part of the negative inotropic action of bupivacaine is the result of inhibition of glucose uptake or utilization in the glycolytic pathway, and further pinpoint the blockade as an early step in the glycolytic sequence prior to the phosphofructokinase step.

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$K^{+}$ channel openers가 기니픽 심근의 수축력, 막전위 및 세포내 $Na^{+}$ 이온 활성도에 미치는 영향

  • 채수완
    • Proceedings of the Korean Society of Applied Pharmacology
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    • 1992.05a
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    • pp.36-36
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    • 1992
  • 기니픽심장에서 유두근을 적출하여 valve 쪽은 silver wire에 연결하여 수축력을 측정하고 mural end는 sylgard floor에 pin으로 고정하여 1Hz로 자극하였다. 이때 사용된 영양액은 Tyrode Ringer로 bath내 은도는 36$^{\circ}C$이고 97% 0$_2$, 3% $CO_2$로 포화시켜 사용하였다. 수축력이 일정해진 후 막전위는 conventional electrode를 이용해서 기록하고, 세포내 $Na^{+}$ 이온 활성도( $a_{Na}$ $^{i}$ )는 $Na^{+}$ 선택적 전극을 이용해서 기록하였다. 적출 기니픽 심근에서 pinacidil, cromakalim, RP49356 둥의 $K^{+}$ channel opener는 활동전위 기간(APD)과 수축력 감소을 일으켰고, pinacidil과 cromakalim에 의한 APD 감소는 glibenclamide (10 $\mu$M)에 의해 거의 억제되었다. Pinacidil, RP49356 및 cromakalim에 의한 수축력 감소시 세포내 $Na^{+}$ 이온농도( $a_{Na}$ $^{i}$ )의 감소가 나타났으며 glibenclamide(10 $\mu$M)에 의한 APD의 감소는 거의 차단되었으나 $a_{Na}$ $^{i}$ 감소는 일부 나타났으며 이때 수축력의 감소도 나타났다.

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Contractile Response of Lidocaine-Depressed Isolated Atria in the Absence of Glucose (Lidocaine에 의해 억제된 적출심방의 수축력에 대한 Glucose제거의 영향)

  • Ko, Kye-Chang;Sohn, Chi-Dong;Park, Seung-Joon;Chung, Joo-Ho;Jung, Jee-Chang;Choi, Seung-Ok
    • The Korean Journal of Pharmacology
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    • v.26 no.2
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    • pp.121-126
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    • 1990
  • The contractility of isolated rat atria, suspended in Krebs-Ringer bicarbonate medium containing 5.5mM glucose, was depressed approximately 50% by 0.1 mM of lidocaine. Partial recovery of the lidocaine-depressed contractility was achieved by the metabolizable substrates pyruvate, acetate, and fructose, but not by addition of glucose. Glucose produced the dose-dependent increase in the force of contraction of normal atria, whereas pyruvate, acetate, and fructose produced no significant effect in the contractile activity of the normal atria. In the absence of exogenous glucose lidocaine produced more marked depression of atrial contractility than that in the presence of exogenous glucose. The results of this study may confirm that the utilization of cardiac glycogen is also inhibited by lidocaine at sites of the glucose phosphate isomerase step or step between glycogen to glucose-6-phosphate.

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Effect of Lidocaine on Utilization of Endogenous Substrates for Contractile Process of Isolated Rat Atria (심근 수축에 쓰여지는 내인성 기질 대사에 대한 Lidocaine의 영향)

  • Ko Kye-Chang
    • The Korean Journal of Pharmacology
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    • v.31 no.1 s.57
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    • pp.53-61
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    • 1995
  • The experiments were performed to determine whether the cardiac depressant action of lidocaine is directly associated with the utilization of endogenous substrates in isolated rat atria, by using citrate and bicarbonate-free medium known as potent inhibitors of phosphofructokinases (PFK) enzyme step. Citrate and bicarbonate-free medium produced negative inotropic action of isolated rat atria incubated in normal Krebs-Ringer bicarbonate glucose medium. Pyruvate and acetate increased the force of contraction of atria depressed by citrate or bicarbonate-free medium, whereas fructose was without effect indicating the inhibitory effect of citrate and bicarbonate-free medium at some point in the glycolytic pathway such as the PFK step in atria. In the absence of exogenous substrate, citrate and bicarbonate-free medium produced a marked depression of the force of substrate-depleted atria indicating that utilization of endogenous substrate above the PFK step, probably cardiac glycogen, is also impaired by citrate or bicarbonate-free medium. Lidocaine produced further depression of the contractile force of atria depressed by citrate. These results argue strongly for an additional mechanism of cardiac depression caused by lidocaine involving the sites below the PFK.

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Changes of Vascular Contraction and Relaxation of Rat aorta under Arsenic Stress (비소 스트레스에 의한 흰쥐 대동맥의 수축과 이완반응의 변화양상)

  • 권윤정;박태규;성유진;김인겸;김중영
    • Journal of Life Science
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    • v.13 no.5
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    • pp.634-641
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    • 2003
  • In order to examine whether arsenic, one of environmental stress, contribute to augumentation and relaxation of rat aorta, this study was performed in vivo and in vitro, using intacted or denuded rats aorta ring preparation, respectively. The carotid arterial pressure was recorded on an ink-writing physiograph(Grass Co. 79E) connected to strain gauge. The contractile response of vascular ring with or without endothelium preparation isolated from rat were determined in organ bath and was recorded on physiograph connected to isometric transducer. Vasopressin-,and phenylephrine- induced increase in arterial pressure significantly enhanced in arsenic-treated rats; increase of 19.1%, and 46.6%, respectively. Vascular contractile response was measured in vitro preparations exposed to 0, 0.5, 1, 2 and 4 mM of arsenic for 1, 3, 5 and 8 hours. The dose-vascular responses of phenylephrine augmented by increasing dose of arsenic in the strips exposed to arsenic for 8 hours, and did not augmented for 1, 3, 5 hours. The phenomenon was not affected by strips denuded endothelium. And the response of relaxation of rat aorta induced by nitroprusside was not influenced by arsenic stress, but acetylcholine was a little increased. compared to that of control. There were no significant difference in relaxation between control and arsenic treated rings with endothelium or denuded. All of the results, phenyleprine-induced vascular contraction was significantly enhanced in 4 mM arsenic-treated rat aortic rings compared with control, whether endothelium was present or denuded at 8 hours after arsenic treatment. It may be a mechanism by which long-term arsenic stresses play a role in development of hypertension.

The Effects of Fructose on Contractility of Isolated Rat Atria Depressed with Lidocaine (Lidocaine에 의해 억제된 심근수축력에 대한 Fructose의 영향)

  • Ko Kye-Chang;Sohn Chi-Dong;Jung Jee-Chang
    • The Korean Journal of Pharmacology
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    • v.22 no.1 s.38
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    • pp.51-59
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    • 1986
  • The effect of metabolic substrate fructose on the force of contraction of isolated rat atria depressed with lidocaine was determined. Fructose produced dose-dependent increase in the force of contraction of isolated atria depressed by substrate-free Krebs-Ringer bicarbonate medium. The maximally effective concentration of fructose was 30 mM. The isolated atria, suspended in Krebs-Ringer bicarbonate glucose medium aerated with 95% $O_2-5%CO_2$at $30^{\circ}C$ and pH 7.4, were depressed 50% by approximately 2.34 mg/100 ml of lidocaine. Addition of 30 mM fructose to these depressed atria resulted in a marked increase in the contractile force similar to that with pyruvate and acetate. Fructose had no significant effect, however, on atria exposed to low-calcium medium. The results are consistent with a previous report suggesting blockade by lidocaine of the uptake or utilization of glucose in the glycolytic pathway, and further pinpoint the blockade as an early step in the glycolytic sequence prior to the phospho-fructokinase step.

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Effect of Strontium on Norepinephrine Induced Positive Intoropic Effect of Isolated Perfused Rat Hearts (흰쥐 적출심장의 Norepinephrine 유발 양성 변력성작용에 미치는 Strontium의 영향)

  • Kwon, Oh-Cheal;Lee, Kwang-Youn
    • Journal of Yeungnam Medical Science
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    • v.5 no.2
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    • pp.59-69
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    • 1988
  • This study was designed to investigate the effect of substitution of strontium for calcium on mechanical activity in isolated perfused spontaneously beating rat hearts. The mechanical activity of the hearts of Langendorff's preparation in conditions of low calcium and strontium-substitution for calcium was compared. The effect of norepinephrine and verapamil were also observed in those conditions. The results were as follows : 1. In low calcium, the mechanical activity of the heart preparation was significantly reduced, but when the equimolar strontium was substituted for the reduced calcium, the activity was kept at similar level to the normal condition. 2. When equimolar strontium was substituted for the total calcium in perfusate, the heart preparation stopped its beating, and it was not restored in spite of reperfusion with normal calcium perfusate. 3. Norepinephrine-induced positive inotropic effect was inhibited in low-calcium condition especially with low concentration of norepinephrine, but not in strontium-substitution for calcium. 4. Verapamil reduced the activity of the heart both in low-calcium and strontium-substitution as well as in normal calcium conditions. From above results, it was concluded that strontium served as a substitute of calcium in maintaining mechanical activity and in responsiveness to norepinephrine, and the influx of strontium through cell membrane is inhibited by verapamil as the influx of calcium.

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Effect of Starvation on Contractility of Lidocaine-Depressed Isolated Rat Atria (Lidocaine 억제 심장의 수축성에 대한 내인성 지질의 영향)

  • Ko, Kye-Chang
    • The Korean Journal of Pharmacology
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    • v.30 no.1
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    • pp.59-65
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    • 1994
  • The experiments were performed to determine whether lidocaine interferes with the utilization of lipid as source of energy fuel for the contractile process by the isolated rat atria. Rats were starved for two days in order to inerease the lipid content of the heart. Atria from starved rats were better able to maintain their contractility in the absence of exgenous substrate, and also were more resistant to depression by lidocaine than atria from fed rats. Starvation results in a marked loss of body weight in rats. In contrast to the starved rats, the body weight of fed rats inereased with time. The smaller reduction in contractile activity of atria from the starved rats may suggest that endogenous lipid accumulates during starvation period and is used as an energy source for the contractile process in the face of a lidocaine-induced blockade in glycolysis.

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Effect of Starvation on Substrate Utilization of Isolated Rat Atria (적출심장의 대사기질 이용에 대한 내인성 기질의 영향에 관한 연구)

  • Ko, Kye-Chang;Chung, Joo-Ho;Jung, Jee-Chang;Sim, Myung-Suk
    • The Korean Journal of Pharmacology
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    • v.29 no.1
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    • pp.57-63
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    • 1993
  • The abilities of metabolic substrates, glucose, pyruvate, and acetate to produce a maximal increase in the force of contraction of substrate-depleted atria from fed rats were compared to those from starved rats, in order to observe the effect of starvation on substrate utilization of the myocardium. Starvation results in a marked loss of body weight in rats. In contrast to the starved rats, the body weight of fed rats increased with time. When placed in substrate-free medium, atria from fed rats showed marked decline in contractile force. In contrast to the atria from fed rats, the substrate-depleted atria from starved rats showed much less decline of the force of contraction. In the substrate-free medium, abilities of glucose, pyruvate, and acetate to produce a maximal increase in the force of contraction of atria from fed rats were much greater than those from starved rats. The data from these studies indicate that in the substrate-free medium atria from starved rats utilize much less exogenous substrates than those from fed rats. These results suggest that starvation has no deleterious effect on contractile activity of the myocardium, and the starvation increase the storage of readily metabolizable endogenous substrstes useful for the functional activity of the isolated heart.

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Measurement of Thermal Shrinkage/Expansion Force of Filled Rubber (충전된 고무재료의 열변화에 따른 수축력/팽창력 측정)

  • Park, Sang-Min;Hong, Chang-Kook;Cho, Dong-Lyun;Kaang, Shin-Young
    • Elastomers and Composites
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    • v.42 no.4
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    • pp.201-208
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    • 2007
  • In this study, the thermal shrinkage and expansion stresses of filled NR and SBR vulcanizates were measured to investigate the dimensional stability at an elevated temperature. When a rubber sample was held at constant pre-strain, a thermal stress developed upon heating due to the entropic consideration. The peak shrinkage stress of carbon black or silica filled NR decreased with increasing filler content. In SBR compounds, however, the peak shrinkage stress of SBR with 30 phr filler content was higher than that of unfilled compounds. The expansion stress of carbon black filled NR was changed little, but that of filled SBR increased with increasing the filler content. The peak expansion stress of silica filled NR and SBR vulcanizates increased with increasing silica content.