• The Korean Journal of Physiology and Pharmacology
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• v.8 no.2
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• pp.95-100
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• 2004

Ischemic preconditioning (IPC) has been accepted as a heart protection phenomenon against ischemia and reperfusion (I/R) injury. The activation of ATP-sensitive potassium $(K_{ATP})$ channels and the release of myocardial nitric oxide (NO) induced by IPC were demonstrated as the triggers or mediators of IPC. A common action mechanism of NO is a direct or indirect increase in tissue cGMP content. Furthermore, cGMP has also been shown to contribute cardiac protective effect to reduce heart I/R-induced infarction. The present investigation tested the hypothesis that $K_{ATP}$ channels attenuate DNA strand breaks and oxidative damage in an in vitro model of I/R utilizing rat ventricular myocytes. We estimated DNA strand breaks and oxidative damage by mean of single cell gel electrophoresis with endonuclease III cutting sites (comet assay). In the I/R model, the level of DNA damage increased massively. Preconditioning with a single 5-min anoxia, diazoxide $(100\;{\mu}M)$, SNAP $(300\;{\mu}M)$ and 8-(4-Chlorophenylthio)-guanosine-3',5'-cyclic monophosphate (8-pCPT-cGMP) $(100\;{\mu}M)$ followed by 15 min reoxygenation reduced DNA damage level against subsequent 30 min anoxia and 60 min reoxygenation. These protective effects were blocked by the concomitant presence of glibenclamide $(50\;{\mu}M)$, 5-hydroxydecanoate (5-HD) $(100\;{\mu}M)$ and 8-(4-Chlorophenylthio)-guanosine-3',5'-cyclic monophosphate, Rp-isomer (Rp-8-pCPT-cGMP) $(100\;{\mu}M)$. These results suggest that NO-cGMP-protein kinase G (PKG) pathway contributes to cardioprotective effect of $K_{ATP}$ channels in rat ventricular myocytes.

• The Korean Journal of Physiology and Pharmacology
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• v.9 no.2
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• pp.95-101
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• 2005

In the heart, $Na^{+}-Ca^{2+}$ exchange (NCX) is the major $Ca^{2+}$ extrusion mechanism. NCX has been considered as a relaxation mechanism, as it reduces global $[Ca^{2+}]_i$ raised during activation. However, if NCX locates in the close proximity to the ryanodine receptor, then NCX would curtail $Ca^{2+}$ before its diffusion to global $Ca^{2+}_i$ This will result in a global $[Ca^{2+}]_i$ decrease especially during its ascending phase rather than descending phase. Therefore, NCX would decrease the myocardial contractility rather than inducing relaxation in the heart. This possibility was examined in this study by comparing NCX-induced extrusion of $Ca^{2+}$ after its release from SR in the presence and absence of global $Ca^{2+}_i$ transient in the isolated single rat ventricular myocytes by using patch-clamp technique in a whole-cell configuration. Global $Ca^{2+}_i$ transient was controlled by an internal dialysis with different concentrations of BAPTA added in the pipette. During stimulation with a ramp pulse from +100 mV to -100 mV for 200 ms, global $Ca^{2+}_i$ transient was suppressed only mildly, and completely at 1 mmol/L, and 10 mmol/L BAPTA, respectively. In these situations, ryanodine-sensitive inward NCX current was compared using $100{\mu}mol/L$ ryanodine, $Na^+$ depletion, 5 mmol/L $NaCl_2$ and $1{\mu}mol/L$ nifedipine. Surprisingly, the result showed that the ryanodine-sensitive inward NCX current was well preserved after 10 mmol/L BAPTA to 91 % of that obtained after 1 mmol/L BAPTA. From this result, it is concluded that most of the NCX-induced $Ca^{2+}$ extrusion occurs before the $Ca^{2+}$ diffuses to global $Ca^{2+})i$ in the rat ventricular myocyte.

• Biomedical Science Letters
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• v.10 no.4
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• pp.385-389
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• 2004

A novel gene Jpk, originally isolated as a trans-acting factor associating with the position-specific regulatory element of murine Hox gene has been reported to be expressed differentially in the liver of diabetic animals. Therefore, in an attempt to develop a possible diagnostic marker and/or new therapeutic agent for the Diabetes Mellitus, we analysed the expression pattern of Jpk among organs of normal and diabetic Sprague-Dawley (SD) rats. Total RNAs were isolated from each organs (brain, lung, heart, liver, spleen, kidney, muscle, blood, and testis) of diabetic and normal rats in both normal feeding and after fasting condition. And then RT (reverse transcription) PCR has been performed using Jpk­specific primers. The Jpk gene turned out to be expressed in all organs tested, with some different expression profiles among normal and diabetes, though. Upon fasting, Jpk expressions were reduced in all organs tested except kidney, muscle and brain of normal rat. Whereas in diabetes, Jpk expressions were increased in all organs except heart, muscle and testis when fasted. Compared to the normal rat, the Jpk expression level in blood was remarkably upregulated (about 15-30times) in diabetic rat whether in normal feeding or fasting conditon, suggesting that the Jpk could be a candidate gene for the possible blood diagnostic marker for the Diabetes Mellitus.

• The Korean Journal of Physiology and Pharmacology
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• v.5 no.5
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• pp.433-441
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• 2001

The ATP-sensitive potassium $(K_{ATP})$) channel is a member of inward rectifier potassium channel (Kir) that is inhibited by intracellular ATP and functions in close relation to sulfonylurea receptors (SUR). Although the molecular mechanism and physiological function of $K_{ATP}$ channels are well understood, the expression pattern during development or treatment with the channel modulators such as glybenclamide is little known. In this work, we determined mRNA levels of a $K_{ATP}$ channel (Kir6.2) and a sulfonylurea receptor (SUR2) in rat tissues by RNase protection assay. Levels of Kir6.2 and SUR2 mRNA in the rat brain and skeletal muscle were higher in adult $(90{\sim}120\;days)$ than in neonate $(2{\sim}8\;days),$ whereas those in the heart were not much different between neonate $(2{\sim}8\;days)$ and adult $(90{\sim}120\;days).$ In addition, none of $K_{ATP}$ channel modulators (opener, pinacidil and nicorandil; blocker, glybenclamide) affected the Kir6.2 mRNA levels in the heart, brain and skeletal muscle. The results indicate that the expression of Kir and SUR genes can vary age-dependently, but the expression of Kir is not dependent on the long-term treatment of channel modulators. The effect of the channel modulators on mRNA level of SUR is remained to be studied further.

• Korean Journal of Pharmacognosy
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• v.13 no.4
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• pp.137-144
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• 1982

It was previously reported from our laboratory that the rate of deterioration of the force of contraction was slower in heart from Panax ginseng extract treated rats. The study carried out to elucidate its mechanism of the action on hearts. The cyclic AMP content in the rat hearts was measured by the method of radioimmunoassay techniques. Panax ginseng extract (100mg/kg/day) was administered orally to male Sprague-Dawley rats weighing 150g to 250g for 1 week and after 24 hrs the hearts were isolated and the cyclic AMP content in the fresh heart was assayed. The difference in cyclic AMP content between the rats treated with Panax ginseng extracts and normal rats was not significant. Panax ginseng extract(l00mg/kg/day) was administered orally to the rats for I week and after 24 hrs the hearts were isolated and perfused with Krebs-Henseleit buffer (pH7.4) for 90min. The cyclic AMP content in the both treated and normal rats was not also significantly different. On the other hand, when total ginseng saponin (50mg/kg/day) was administered orally to rats for 1 week and after 24 hrs, the isolated hearts were perfused with Krebs Henseleit solution for 32min, the cyclic AMP content in total ginseng soponin treated hearts was decreased by 18.7% compared to normal rats. It was also observed that when isolated hearts were perfused with total ginseng saponin $(10^{-4}g/ml)$ for 12 min after 30 min equilibration period, the cyclic AMP content in total ginseng saponin treated hearts was decreased by 23.7% compared to normal rats. Isolated hearts were perfused with ginseng saponins $(10^{-4}g/ml)$ or with Krebs-Henseleit solution alone for 10min and subsequently with dl-isoproterenol $(1/2{\times}10^{-6}M)$ until the positive inotropic effect of isoproterenol was initiated. The cyclic AMP content in each rat hearts treated with total ginseng saponin, or with ginsenoside $Rb_1$, or with Krebs-Henseleit solution alone were increased by 35.5%, 42.4%, 47.5%, respectively, compared to normal rats.

• YAKHAK HOEJI
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• v.29 no.4
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• pp.199-205
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• 1985

It was previously reported that the deterioration rate of contractile force of the isolated heart from ginseng extract treated rat was slower than that from control. Present study was carried out to investigate the mechanism of the action of ginseng on the contractile force of the papillary muscle in terms of calcium metabolism. Rats weighing 200-300g were administered orally with ginseng ethanol extract (100mg/kg/day) for more than 10 days. The isolated papillary muscles from rat hearts were suspended in bath containing Krebs-Henseleit solution. When equilibration of contractile force of papillary muscle was reached, the rates of deterioration of contractile forces of papillary muscle from ginseng component treated rats were determined by washing with Ca-free Krebs-Henseleit solution and compared with that of normal hearts. At the beginning of washing, the rate of deterioration of contractile force of the papillary muscle was slower significantly in ginseng treated rats than in control rats, suggesting that calcium may be somehow involved in sustaining the contractility in ginseng treated hearts. Anoxia of papillary muscle with nitrogen gas to muscles inhibited the contractility, but differences between control and ginseng treated groups in the rate of deterioration were not observed. Influence of diltiazem, calcium blocker, on the contractility of papillary muscle from ginseng treated and control hearts was studied. Contractility of papillary muscle from control and ginseng treated hearts was inhibited by diltiazem in dose dependent manner but the inhibition of the ginseng treated muscles was much weak. The effect was significantly different. From the results, it seemed that slowing in deterioration rate of papillary muscle from ginseng treated hearts might be related to calcium which was mobilized from plasma membrane of internal organelle by ginseng.

• Nutritional Sciences
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• v.8 no.1
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• pp.16-22
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• 2005

The present study examined the effects of cyclooxygenase-2 (COX-2) inhibitor celecoxib or soy-isoflavones in the presence of estrogen on apoptosis related gene expression, COX-2 and mapkinase in 48-week old female rats. Expressions of bel-2 and bax proteins, which are known to be involved in the regulation of apoptosis, were investigated in mammary glands and heart tissues. The elevated expression of bel-2 expression was observed in mammary glands of celecoxib supplemented rats as well as soy-isoflavones. The mammary glands bel-2/bax ratio was found to be higher in celecoxib or soy-isoflavones supplemented rats. However, in heart tissues, expression of bel-2 and bax was in the order of control, celecoxib and soy-isoflavones. The up-regulation of COX-2 was observed in celecoxib or soy-isoflavones in mammary glands. 'The similar trend was not displayed with the mapkinase expression. In heart tissues, the down-regulation of COX-2 as well as mapkinase was observed in celecoxib or soy-isoflavones supplemented rats. Soy-isoflavones and celecoxib both had a similar regulatory pattern of bel-2, bax and COX-2 in mammary glands, and in heart tissues, only COX-2 exhibited a similar down-regulatory properly. These findings revealed that in estrogen sufficient state, celecoxib and soy-isoflavones might not exhibit proapoptotic potential or COX-2 inhibition in normal mammary glands.

• Biomolecules & Therapeutics
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• v.7 no.4
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• pp.354-361
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• 1999

In this study, the effects of tauroursodeoxycholic acid (TUDCA) on ischemia/ reperfusion injury were investigated on isolated heart perfusion models. Hezrts were perfused with oxygenated Krebs-henseleit solution (pH 7.4, $37^{\cire}C$) on a Langendorff apparatus. After equilibration, isolated hearts were treated with TUDCA 100 and 200 $\mu\textrm{M}$ or vehicle (0.02% DMSO) for 10 min before the onset of ischemia in single treatment group. In 7 day pretreatment group. TUDCA 50, 100 and 200 mg/kg body weight were given orally for 7 days before operation. After global ischemia (30 min), ischemic hearts were reperfused for 30 min. The physiological (i.e. heart rate, left ventricdular developed pressure, coronary flow, double product, time to contracture formation) and biochemical (lactate dehydrogenase; LDH) parameters were evaluated. In vehicle-treated group, time to contracture formation was 810 sec during ischemia, LVDP was 34.0 mmHg at the endpoint of reperfusion and LDH activity in total reperfusion effluent was 34.3 U/L. Single treatment with TUDCA did not change the postischemic recovery of cardiac function, LDH and time to contractur compared with ischemic control group. TUDCA pretreatment showed the tendency to decrease LDH release and to increase time to contracture and coronary flow. Our findings suggest that TUDCA does not ameliorate ischemia/reperfusion-reduced myocardial damage.

• Journal of Chest Surgery
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• v.17 no.4
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• pp.565-573
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• 1984

The increasing use of cardioplegic solution for the reduction of ischemic tissue injury requires that all cardioplegic solution be carefully assessed for any protective or damaging properties. This study describes functional assessment of the efficiency of steroid in cardioplegic solution by using a Langendorffs perfusion model. Isolated rat heart were subject to a 2 minute period of coronary infusion with the steroid mixed cold cardioplegic solution immediately before and also at the midpoint of a 60 minutes period of hypothermic [10\ulcorner\ulcorner] ischemic arrest. The result of this study were as follows: 1.Spontaneous heart beat after ischemic arrest occurred 14 second later Langendorffs reperfusion in the steroid mixed Young & GIK group and 16 second later in the control group. [Young & GIK without steroid] A good recovery state of spontaneous heart beat was shown in both groups. 2.The percentage of recoveries of heart rate during the 30 minute after postischemic Langendorffs reperfusion was; at first 5 minute 106.3\ulcorner.7% [P<0.05] in the steroid mixed Young & GIK group. This percentage of recovery of steroid mixed Young & GIK group was significantly greater than the control group during the first 5 minute course. 3.The percentage of recovery of coronary flow during the 30 minute after postischemic Langendorffs reperfusion was; at first 5 minute 101\ulcorner.2% in the steroid mixed Young & GI K group. This percentage of recovery of the steroid mixed Young & GIK group was not significantly than the control group during the first 5 minute.

• Archives of Pharmacal Research
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• v.22 no.5
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• pp.479-484
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• 1999

In this study, the effects of ursodeoxycholic acid (UDCA) on ischemia/reperfusion injury were investigated on isolated heart perfusion model. Hearts were perfused with oxygenated Krebs-Henseleit solution (pH 7.4, $37^{\circ}C$) on a Langendroff apparatus. After equilibration, isolated hearts were treated with UDCA 20 to 160 $\mu$M or vehicle (0.04% DMSO) for 10 min before the onset of ischemia. After global ischemia (30 min), ischemic hearts were reperfused and allowed to recover for 30 min. The physiological (i.e. heart rate, left ventricular developed pressure, coronary flow, double product and time to contracture formation) and biochemical (lactate dehydrogenase; LDH) parameters were evaluated. In vehicle-treated group, time to contracture formation was 21.4 min during ischemia, LVDP was 18.5 mmHg at the endpoint or reperfusion and LDH activity in total reperfusion effluent was 54.0 U/L. Cardioprotective effects of UDCA against ischemia/reperfusion consisted of a reduced TTC $(EC_{25}=97.3{\mu}M)$, reduced LDH release and enhanced recovery of cardiac contractile function during reperfusion. Especially, the treatments of UDCA 80 and $160 {\mu}M $ significantly increased LVDP and reduced LDH release. Our findings suggest that UDCA ameliorates ischemia/reperfusion-induced myocardial damage.