ABSTRACT
Objective To investigate the relationship between alteration of gene in cyclic adenosine monophosphate(cAMP) signal transduction system in rats after myocardial damage and changes of cardiac function and ventricular remodeling. Methods Twenty eight male Wistar rats weighing 220 g to 250 g were randomly divided into three groups: acute myocardial damage group(AMD, n = 10), chronic myocardial damage group (CMD,n = 9 ) and sham-operation group (control, n = 9). Animal model of acute myocardial damage was established by ligation of rats left coronary artery in the AMD and the CMD groups. Rats in control group were treated similarly, except that the coronary suture was not tied. Hemodynamics and echocardiography were measured before rats were sacrificed 24 hours after operation in control and AMD groups but those in CMD groups were sacrificed 8 weeks later. Cadiocyte apoptosis were estimated by TUNEL method, cAMP levels in heart were tested by radioimmunity and the mRNA expressions for inducible cAMP early repressor (ICER), cAMP response element binding protein (CREB), phosphodiesterase 3A (PDE3A) and bcl-2 were assayed by real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Results The difference of left ventricular end diastolic diameter (LVEDD), left ventricular end diastolic pressure(LVEDP), maximal rising and falling rate of ventricular pressure,left ventricular systolic pressure (LVSP), eject fraction (EF) and fraction shortening (FS) were statistically significant among the three groups(F = 285.9, 196.8, 83.2, 80.4, 54.9, 196.6, 95.2, all P ＜ 0.01). LVEDD[(7.03 ±0.28), (8.20 ± 0.27)mm] and LVEDP[(11.19 ± 2.89), (19.76 ± 3.34)mmHg] in AMD and CMD groups were significantly increased, compared with those in control group[ (5.05 ± 0.30)mm, (- 5.62 ± 3.01 )mmHg, all P ＜0.01 ]. While maximal rising rate[ (2964 ± 449), (2214 ± 434)mmHg/s] and falling rate[(- 2617 ± 441),(- 1891± 424)mmHg/s] of left ventricular pressure, LVSP[ (94.19 ± 4.03), (85.85 ± 6.39)mmHg], EF[ (41.6 ±5.9)%, (35.9 ± 4.1 )%] and FS[ (36.9 ± 4.6)%, (23.1 ± 4.9)%] of left ventricular in the two groups were lower than those in control[(4759 ± 406)mmHg/s, (- 4327 ± 388)mmHg/s, (116.29 ± 8.25)mmHg, (80.9 ± 5.6)%,(53.1 ± 4.3)%, all P ＜ 0.01 ]. These changes in CMD group were more significant than those in AMD groups(P ＜0.05 or P ＜ 0.01 ). The difference of apoptotic index, cAMP and expression of ICER, CREB, PDE3A mRNA and bcl-2 mRNA were statistically significant among the three groups(F= 172.5, 141.0, 540.8, 246.8, 165.1, 563.9,all P＜ 0.01 ). Apoptotic index[ (32.8 ± 4.2)‰, (18.4 ± 3.9)‰] and cAMP in heart[ (9.95 ± 0.30), (5.60 ± 0.25)nmol/kg] in AMD and CMD groups were increased compared to control group[ (3.9 ± 1.7)‰, (2.48 ± 0.29)nmol/kg,all P ＜ 0.01 ], and those in CMD group were lower than in AMD group(all P ＜ 0.01 ). Expression of ICER mRNA (1.434 ± 0.093, 0.942 ± 0.076) and CREB mRNA(5.70 ± 0.50, 2.64 ± 0.51) in AMD and CMD groups were higher, and expression of PDE3A mRNA(48.98 ± 8.14, 16.68 ± 8.46) were lower than those in control group (0.154 ± 0.063, 1.08 ± 0.35, 105.94 ± 12.61, all P ＜ 0.01 ). The three genes in CMD group were fewer than those in AMD group(all P ＜ 0.01 ). bcl-2 mRNA was up regulated in AMD group(4.55 ± 0.27) and was down regulated in CMD group(0.35 ± 0.15) compared to control(2.18 ± 0.30, all P＜ 0.01). Conclusions There is PDE3A-ICER positive-feedback loop leading to myocyte apoptosis and heart failure after myocardial damage. The downregulation of PDE3A mRNA observed in chronic myocardial damage may play a causative role in the progression of ventricular remodeling and heart failure, in part, by inducing ICER mRNA and promoting cardiac myocyte dysfunction.
ABSTRACT
The present study aimed to explore whether the stretch of ischemic myocardium could modulate the electrophysiological characteristics via mechanoelectric feedback (MEF), as well as the effect of phalloidin on the electrophysiological changes. Thirty-two Wistar rats were randomly divided into 4 groups: control group (n=9), phalloidin group (n=7), myocardial infarction (MI) group (n=9), MI + phalloidin group (n=7). The acute myocardial infarction (AMI) was conducted by ligation of the left anterior descending (LAD) coronary artery for 30 min in isolated rat heart. The volume alternation of a water-filled latex balloon in the left ventricle produced the stretch of myocardium. After perfused on Langendorff, the isolated hearts were stretched for 5 s by an inflation of 0.1, 0.2 and 0.3 mL separately and the effect of stretch was observed for 30 s, including the left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), ±dp/dt(max), monophasic action potential duration at 90% repolarization (MAPD90), and occurrence of premature ventricular beats (PVB) and ventricular tachycardia (VT). The stretch caused an increase of MAPD(90) in both control and MI rats (P<0.05, P<0.01). Moreover, MAPD(90) in MI group increased more significantly than that in the control group at the same degree of stretch (P<0.05, P<0.01). Phalloidin (1 μmol/L) had no effect on MAPD(90) in basal state. After stretch, MAPD(90) in phalloidin group slightly increased but was not significantly different from that in the control group. However, phalloidin reduced MAPD(90) in infarcted myocardium, especially when ΔV=0.3 mL (P<0.05). The incidence rates of PVB and VT in MI group were higher than that in the control group (both P<0.01). And there was no significant difference in the incidence rates of PVB and VT between phalloidin group and control group. Phalloidin inhibited the occurrence of PVB and VT in infarcted hearts (both P<0.01). LVSP and +dp/dt(max) in MI group obviously decreased (P<0.01 vs control). With application of phalloidin, LVSP slightly, but not significantly increased in infarcted hearts, while -dp/dt(max) significantly increased (P<0.05). It is suggested that MI facilitates the generation and maintenance of malignant arrhythmias, while phalloidin obviously inhibits the occurrence of arrhythmias.
Subject(s)
Animals , Rats , Action Potentials , Arrhythmias, Cardiac , Coronary Vessels , Heart , Heart Ventricles , Myocardial Infarction , Phalloidine , Pharmacology , Rats, WistarABSTRACT
<p><b>OBJECTIVE</b>To observe the changes of plasma renin activity, antidiuretic hormone and brain natriuretic peptide in chronic heart failure (CHF) and their correlation with hyponatremia.</p><p><b>METHODS</b>Plasma levels of PRA, ADH, and BNP were measured by radioimmunology in 76 CHF patients. Forty-one out of 76 CHF patients with hyponatremia and 35 CHF patients without hyponatremia were identified by serum sodium. The rates of rehospitalization within 3 months were compared in two groups.</p><p><b>RESULTS</b>Levels of plasma renin activity, ALD, and BNP in CHF patients with hyponatremia were notably higher than those in patients without hyponatremia classified by New York Heart Association (NYHA) grade II - IV: PRA [(2.7 +/- 1.0) ng.ml(-1).h(-1) vs. (1.8 +/- 0.7) ng.ml(-1).h(-1), (4.3 +/- 1.2) ng.ml(-1).h(-1) vs. (3.0 +/- 0.9) ng.ml(-1).h(-1), (5.6 +/- 1.3) ng.ml(-1).h(-1) vs. (3.5 +/- 1.1) ng.ml(-1).h(-1), respectively, P < 0.05], ADH [(59.7 +/- 17.4) ng/L vs. (48.6 +/- 15.3) ng/L, (68.4 +/- 17.6) ng/L vs. (56.3 +/- 19.2) ng/L, (75.3 +/- 20.0) ng/L vs. (51.4 +/- 16.2) ng/L, respectively, P < 0.05] and BNP [(276.4 +/- 75.2) ng/L vs. (185.3 +/- 55.3) ng/L, (380.1 +/- 113.6) ng/L vs. (258.5 +/- 62.1) ng/L, (564.0 +/- 125.2) ng/L vs. (405.3 +/- 102.9) ng/L, respectively, P < 0.05]. In the simple regression analyses, hyponatremia was negative correlated with PRA, ADH and BNP (r = -0.31, P < 0.05; r = -0.28, P < 0.05, r = -0.80, P < 0.01). The rate of rehospitalization within 3 months in hyponatremia group was higher than that in control group.</p><p><b>CONCLUSIONS</b>There is relation of hyponatremia to the changes of plasma renin activity, antidiuretic hormone and brain natriuretic peptide in chronic heart failure. Hyponatremia may accelerate the excretion of plasma PRA, ADH and BNP in chronic heart failure. Neuroendocrine activation in patients of congestive heart failure with hyponatremia is higher than that of normal natremia group.</p>