[Effects of Evan Blue on perfused dimension display and rabbit left ventricular action potential].

OBJECTIVE: Simultaneous recording of transmembrane action potential at endocardium, midcardium and epicardium and transmural ECG in arterially perfused left ventricular preparation is a new method for researching into the mechanism about ventricular arrhythmia, and in this connection, how to distinguish the perfused area plays a key role in keeping preparations under normal condition. This study is aimed to evaluate the effects of Evan Blue on the displaying of the perfused area and on the characters of transmembrane action potential of the arterially perfused left ventricular preparations. METHODS: Rabbit left ventricular wedge preparations were perfused with Tyrode solution continuously via left circumflex, and the action potential of endocardium, midmyocardium, epicardium or transmural electrocardiogram were recorded simultaneously. The action poatential duration (APD), transmural dispersion of repolarization (TDR) or QT intervals were compared and the color variation of the preparations were studied before and 30 min after perfusion with Evan Blue. RESULTS: Under the basic stimulatory cycle length of 1000, 2000, 4000 ms, there was no significant difference of APD in the same transmural layer or TDR before and after Evan Blue perfusion (P<0.01), but APD or TDR stimulated at basic cycle length of 1000-4000 ms were all higher than those recorded at 500 ms (P<0.01); APDs of endocardium were much longer than those of epicardium or midmyocardium (P<0.01); there was no significant difference in APD, TDR and QT intervals before and after Evan Blue perfusion (P>0.05). No premature ventricular contractions and ventricular tachycardia happened during the experiments. CONCLUSION: Evan Blue can be used as a marker to identify the perfused area.

[Heterogeneity of Na+/Ca2+ exchanger current across the left ventricular wall of rabbit].

OBJECTIVE: To investigate the distribution characteristics of Na+/Ca2+ exchanger current (I(Na+/Ca2+)) across the left ventricular wall of rabbit and the relationship between I(Na+/Ca2+) and transmural depolarization heterogeneity. METHODS: By using whole-cell patch clamp techniques, action potentials (AP), I(Na+/Ca2+), and both rapid and slow components of delayed rectifier potassium current (I(Kr) and I(Ka)) were recorded in subendocardial (Endo), midmyocardial (M), and subepicardial (Epi) cells of the left ventricular wall of rabbit. RESULTS: AP duration in M cells was longer than that in Epi cells, P<0.01. At the test potential of +40 mV, outward I(Na+/Ca2+) in M cells was larger than that in Epi and Endo cells, P<0.01, P<0.05, respectively. At the test potential of -100 mV, inward I(Na+/Ca2+) in M cells was larger than that in Epi cells, P<0.05. At the test potential of +50 mV, the tail current density of I(Ka) in M cells was smaller than that in Epi cells, P<0.05, and there was no significant difference among the tail current densities of I(Kr) in Endo, M, and Epi cells. CONCLUSION: The distribution of I(Na+/Ca2+) and I(Ka) across the left ventricular wall of rabbit is unequal, which contributes to the transmural depolarization heterogeneity.

Adrenergic receptor antagonist prevents the left ventricle with chronic pressure-overload from electrical remodeling.

Experiments were performed to investigate the effects of long-term treatment with adrenergic receptor antagonist on electrical remodeling of the left ventricle with chronic pressure-overload. New Zealand rabbits underwent subtotal banding of superrenal abdominal aorta. At 10 weeks after surgery, echocardiography examination was performed, then action potential (AP), inward rectifier potassium current (I(Ki)), delayed rectifier potassium current (I(K)) and Na(+)/Ca(2+) exchanger current (I(Na(+)/Ca(2+))) were recorded in midmyocardial cells isolated from left ventricle of abdominal aorta banded group (banded group), abdominal aorta banding plus Carvedilol intervention group (Carvedilol group), and normal control group rabbits by using the whole-cell patch-clamp techniques. The results showed that left ventricular mass index in control, banded, and Carvedilol groups were 1.78+/-0.06 (n=7), 2.33+/-0.11 (n=7), and 1.87+/-0.08 (n=7), respectively (banded vs control and Carvedilol, P<0.01). At basic cycle length of 2 s, AP duration (measured at 90% repolarization, APD(90), ms) in control, banded, and Carvedilol groups were 522.0+/-19.5 (n=6), 664.7+/-46.2 (n=7), 567.8+/-14.3 (n=8) respectively (banded vs control, P<0.01; Carvedilol vs banded, P<0.05). At test potential of -100 mV, inward I(Ki) density (pA/pF) in control, banded, and Carvedilol groups were -11.8+/-0.50 (n=8), -8.07+/-0.28 (n=8), -10.69+/-0.35 (n=8) respectively (banded vs control and Carvedilol, P<0.01). At test potential of +50 mV, I(K) tail current density (pA/pF) in control, banded, and Carvedilol groups were 0.59+/-0.04 (n=8), 0.40+/-0.02 (n=9), 0.51+/-0.02 (n=8) respectively (banded vs control, P<0.01; Carvedilol vs banded, P<0.05). At test potential of +60 mV, outward I(Na(+)/Ca(2+)) density (pA/pF) in control, banded, and Carvedilol groups were 1.06+/-0.11 (n=8), 1.54+/-0.10 (n=9), 1.24+/-0.07 (n=8), respectively (banded vs control and Carvedilol, P<0.01). At test potential of -120 mV, inward I(Na(+)/Ca(2+)) density (pA/pF) in control, banded, and Carvedilol groups were -0.54+/-0.06 (n =8), -0.75+/-0.04 (n=9), -0.60+/-0.03 (n=8), respectively (banded vs control, P<0.01; Carvedilol vs banded, P<0.05). It is shown that long-term treatment with Carvedilol not only prevents development of cardiac hypertrophy, but also improves the electrophysiological alterations in rabbit hearts with chronic pressure-overload. This finding may add new electrophysiological evidence for the treatment of heart failure and hypertension with adrenergic receptor antagonist.

[Na+/Ca2+ exchanger current and K+ current remodeling in midmyocardial cells of hypertrophic left ventricle].

OBJECTIVE: To investigate the characteristics of Na+/Ca2+ exchanger current (INa+ /Ca2+) and K+ current remodeling in midmyocardial cells of hypertrophic left ventricle for understanding the ionic basis of arrhythmia of the hypertrophic heart. METHODS: Twenty New Zealand rabbits were divided equally into normal control group and operation group, and in the latter, left ventricular hypertrophy was induced in the rabbits by partial ligation of the abdominal aorta. Action potentials, INa+/Ca2+, slowly activating delayed rectifier K+ current (IKs) and rapidly activating delayed rectifier K+ current (IKr) were recorded in the two groups by using whole-cell patch-clamp technique. RESULTS: At the basic cycle length of 2 s, 90% action potential duration (APD90) in control and operation groups was 522.0+/-19.5 ms (n=6) and 664.7+/-32.7 ms (n=7) respectively; at the testing potential of +40 mV, outward INa+/Ca2+ density in the two groups was 0.94+/-0.11 pA/pF (n=9) and 1.30+/-0.11 pA/pF (n=8) respectively; the testing potential of -100 mV elicited inward INa+/Ca2+ density of 0.40+/-0.05 pA/pF (n=9) and 0.56+/-0.02 pA/pF (n=8) respectively. The testing potential of +50 mV induced IKs tail current density of 0.26+/-0.03 pA/pF (n=8) and 0.17+/-0.01 pA/pF (n=9), and IKr tail current density of 0.34+/-0.02 pA/pF (n=8) and 0.23+/-0.02 pA/pF (n=9) respectively. Statistically significant differences were identified between the control and operation groups in all the above indices measured. CONCLUSION: The characteristics of electrical remodeling changes in midmyocardial cells of hypertrophic left ventricle, exhibited by prolonged action potential, up-regulated INa+/Ca2+ and down-regulated IKs and IKr.

Curcumin ameliorates left ventricular function in rabbits with pressure overload: inhibition of the remodeling of the left ventricular collagen network associated with suppression of myocardial tumor necrosis factor-alpha and matrix metalloproteinase-2 expression.

OBJECTIVE: Curcumin is a wide-spectrum cellular protector with antiinflammatory, antioxidizant, and antifibrotic effects. This study was conducted to investigate its effects on myocardial collagen remodeling in pressure overloaded rabbits. METHODS AND RESULTS: Pressure overloaded rabbits were established by partial abdominal aorta ligation. The rabbits were divided into the sham-operation group, vehicle group and curcumin group. Curcumin was administered orally at a dose of 100 mg/kg.d in 10 ml of 2.5% polyethylene glycol solution and the other 2 groups were given the same dose of polyethylene glycol solution. Compared with the vehicle group, left ventricular function in the curcumin group was significantly ameliorated, as indicated by decreased left ventricular end-diastolic pressure, left ventricle weight to body weight ratio, and the left ventricular posterior wall thickness. The collagen volume fraction in the curcumin group was also reduced. Myocardial tumor necrosis factor (TNF)-alpha and matrix metalloproteinase (MMP)-2 expression were significantly overexpressed in the vehicle group and markedly suppressed in the curcumin group at both the 4th and 8th weeks. At the end of the 8th week, the ejection fraction in the curcumin group was increased compared with that in the vehicle group. CONCLUSION: Curcumin improved left ventricular function in pressure overloaded rabbits. This might be due to inhibition of collagen remodeling associated with suppression of myocardial expression of tumor necrosis factor-alpha, and matrix metalloproteinase-2.

[Effect of xuezhikang on blood lipids, serum oxidized low density lipoprotein, C-reactive protein and fibrinogen in patients with unstable angina pectoris].

OBJECTIVE: To study the lipid regulatory effect of Xuezhikang (XZK) and its effects on serum oxidized low density lipoprotein (OX-LDL), C-reactive protein (CRP) and fibrinogen (FIB) in patients with unstable angina pectoris (UAP). METHODS: UAP patients with hyperlipidemia were treated with XZK 0.6 g, orally taken, twice a day for 2 successive months followed by half dosage for 2 months. To UAP patients with normal blood lipids, Vit E was given orally for 4 months. Levels of blood lipids, OX-LDL, CRP, FIB at the time of entry, 1st and 2nd month of the therapeutic course were observed and end-point events in the two groups was compared. RESULTS: XZK can reduce the serum level of total cholesterol, low density lipoprotein after being administered for 1 month, and the effect further elevated after 2 months. Its effect in lowering triglycerides and increasing high density lipoprotein initiated after 2 months administration. Compared with effect of Vit E, XZK can significantly lower the serum OX-LDL, CRP and FIB after 2 months administration, and reduce the end-point events in 4 months. CONCLUSION: XZK has good regulatory effect on blood lipids, it also can inhibit the development of inflammation in coronary plaque, therefore, is beneficial to the prognosis of UAP patients.