enalaprilat-anhydrous and Reperfusion-Injury

Chronic angiotensin-converting enzyme inhibitor (ACEIs) treatment can suppress arrhythmogenesis. To examine whether the effect is more immediate and independent of suppression of pathological remodelling, we tested the antiarrhythmic effect of short-term ACE inhibition in healthy normotensive rats. Wistar rats were administered with enalaprilat (ENA, i.p., 5 mg/kg every 12 h) or vehicle (CON) for 2 weeks. Intraarterial blood pressure in situ was measured in A. carotis. Cellular shortening was measured in isolated, electrically paced cardiomyocytes. Standard 12-lead electrocardiography was performed, and hearts of anaesthetized open-chest rats were subjected to 6-min ischemia followed by 10-min reperfusion to examine susceptibility to ventricular arrhythmias. Expressions of calcium-regulating proteins (SERCA2a, cardiac sarco/endoplasmic reticulum Ca(2+)-ATPase; CSQ, calsequestrin; TRD, triadin; PLB, phospholamban; Thr(17)-PLB-phosphorylated PLB at threonine-17, FKBP12.6, FK506-binding protein, Cav1.2-voltage-dependent L-type calcium channel alpha 1C subunit) were measured by Western blot; mRNA levels of L-type calcium channel (Cacna1c), ryanodine receptor (Ryr2) and potassium channels Kcnh2 and Kcnq1 were measured by qRT-PCR. ENA decreased intraarterial systolic as well as diastolic blood pressure (by 20%, and by 31%, respectively, for both P < 0.05) but enhanced shortening of cardiomyocytes at basal conditions (by 34%, P < 0.05) and under beta-adrenergic stimulation (by 73%, P < 0.05). Enalaprilat shortened QTc interval duration (CON 78 ± 1 ms vs. ENA 72 ± 2 ms; P < 0.05) and significantly decreased the total duration of ventricular fibrillations (VF) and the number of VF episodes (P < 0.05). Reduction in arrhythmogenesis was associated with a pronounced upregulation of SERCA2a (CON 100 ± 20 vs. ENA 304 ± 13; P < 0.05) and complete absence of basal Ca(2+)/calmodulin-dependent phosphorylation of PLB at Thr(17). Short-term ACEI treatment can provide protection against I/R injury-induced ventricular arrhythmias in healthy myocardium, and this effect is associated with increased SERCA2a expression.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Arrhythmias, Cardiac; Blotting, Western; Calcium Channels, L-Type; Cell Separation; Electrolytes; Enalaprilat; Heart Ventricles; Isoproterenol; Male; Myocardial Contraction; Myocardium; Myocytes, Cardiac; Organ Size; Potassium Channels; Rats, Wistar; Reperfusion Injury; RNA, Messenger; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Ultrasonography; Up-Regulation

Based on clinical and experimental studies, angiotensin II receptor blockers and angiotensin converting enzyme inhibitors have been proposed to exert acute anti-arrhythmic effects in heart failure patients. Therefore, the goal of this study was to assess acute anti-arrhythmic effects of losartan and enalaprilat in hypertrophied rat hearts during low-flow ischaemia and reperfusion. In dose-finding experiments in non-hypertrophied isolated perfused hearts, we performed dose-response curves of losartan and enalaprilat studying monophasic action potential duration at 90% repolarisation (MAPD(90%)) and ventricular fibrillation (VF) threshold. Subsequently, we determined the effects of losartan and enalaprilat (in therapeutically relevant concentrations) on ventricular tachyarrhythmias induced by low-flow ischaemia/reperfusion in hearts demonstrating left ventricular (LV) hypertrophy 70 days after aortic banding. We found that neither drug significantly affected MAPD(90%) (1 nM-1 mM) or VF threshold (1 microM losartan and 10 microM enalaprilat) in non-hypertrophied hearts. Similarly in hypertrophied hearts, neither drug significantly affected the incidence or the duration of ventricular tachyarrhythmias (ventricular tachycardia and VF) during low-flow ischaemia. However, 1 microM losartan significantly reduced the duration of ventricular tachyarrhythmias during reperfusion. In conclusion, neither losartan nor enalaprilat is acutely anti-arrhythmic in hypertrophied rat hearts during low-flow ischaemia. During reperfusion, however, losartan but not enalaprilat exerts acute anti-arrhythmic effects.

Topics: Action Potentials; Animals; Anti-Arrhythmia Agents; Dose-Response Relationship, Drug; Enalaprilat; Heart; Hypertrophy, Left Ventricular; In Vitro Techniques; Losartan; Male; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Tachycardia, Ventricular; Ventricular Fibrillation

The stress-responsive mitogen-activated protein kinases (MAPKs) (p38-MAPK, c-Jun NH2-terminal kinase [JNK-1 and JNK-2], and extracellular signal regulated kinases [ERK-1 and ERK-2]) might be involved in angiotensin II (AII)-induced ischemia-reperfusion injury. Cardioprotection induced by AII type 1 (AT1) and type 2 (AT2) receptor blockade during ischemia-reperfusion is associated with protein kinase Cepsilon (PKCepsilon), nitric oxide, and cyclic guanosine monophosphate (cGMP) signaling. Our aim was to assess the effect of selective AT1 and AT2 receptor blockade with losartan and PD123,319, respectively, on MAPK expression after ischemia-reperfusion in isolated working rat hearts.. Groups of six hearts were subjected to global ischemia (30 minutes) followed by reperfusion (30 minutes) and exposed to no drug/no ischemia-reperfusion (control), ischemia-reperfusion/no drug, and ischemia-reperfusion with losartan (1 microM), or PD123,319 (0.3 microM) and additional groups. AT1/AT2 receptor expression, MAPKs, PKCepsilon, and cGMP, and changes in mechanical function were measured. Western blotting was done on left ventricular tissue for AT1/AT2, p38/phosphorylated-p38 (p-p38), phosphorylated (p)-JNK-1/-2, phosphorylated (p)-ERK-1/-2, and PKCepsilon proteins; Northern blots for AT1/AT2 mRNA; and enzyme immunoassay for cGMP.. Compared with controls, ischemia-reperfusion induced significant left ventricular dysfunction, decreased AT2 protein and mRNA, increased p-p38 and p-JNK-1/-2, did not change p-ERK-1/-2 or PKCepsilon, and decreased cGMP. PD123,319 improved left ventricular recovery after ischemia-reperfusion, increased AT2 protein and mRNA, mildly increased p-p38, normalized p-JNK-1, did not change p-ERK-1/-2, and increased PKCepsilon and cGMP. Losartan did not change p-p38, increased p-JNK-1, and did not change pERK-1/-2, PKCepsilon, or cGMP.. The overall results suggest that the activation of p38-MAPK and JNK might be linked to AII signaling and play a significant role in acute ischemia-reperfusion injury as well as in the cardioprotective effect of AT2 receptor blockade.

Topics: Angiotensin II Type 2 Receptor Blockers; Animals; Antihypertensive Agents; Blood Pressure; Cardiac Output; Coronary Circulation; Cyclic GMP; Disease Models, Animal; Enalaprilat; Enzyme Activation; Heart; Losartan; Male; Mitogen-Activated Protein Kinases; Models, Cardiovascular; Phosphorylation; Protein Kinase C; Protein Kinase C-epsilon; Rats; Rats, Sprague-Dawley; Reperfusion Injury; RNA, Messenger

Chronic angiotensin-converting enzyme (ACE) inhibition initiated days to weeks after acute myocardial infarction can reduce ventricular dilatation and improve patient survival. However, the effects on coronary vascular and myocardial function of very early ACE inhibitor therapy for acute myocardial infarction remain unresolved.. Hemodynamics, segmental shortening, coronary blood flow, and in vitro coronary microvascular relaxation responses were studied in noninstrumented control pigs (n = 8) and pigs subjected to 30 minutes of left anterior descending ischemia followed by administration of 30 mL IV normal saline (IR-saline, n = 8), 5 mg/kg IV captopril (IR-captopril, n = 6), or 1.5 mg/kg IV enalaprilat (IR-enalaprilat, n = 6) before 1 hour of reperfusion. Hemodynamics were similar at baseline, end of ischemia, and end of reperfusion. However, coronary blood flow immediately on reperfusion was significantly enhanced in the IR-enalaprilat cohort (59 +/- 10 mL/min) compared with the IR-saline group (32 +/- 3 mL/min, P < .05). Segmental shortening in the dyskinetic ischemic region improved only minimally at the end of reperfusion to 1 +/- 2%, -7 +/- 3%, and -2 +/- 6% for the IR-saline, IR-captopril, and IR-enalaprilat groups, respectively (P < .05, IR-captopril versus IR-saline). Arteriolar microvascular endothelium-dependent responses to ADP (P < .01) and calcium ionophore A23187 (P < .01) were impaired after ischemia-reperfusion, whereas bradykinin responses were preserved (P = .95). Endothelium-dependent venular responses to ADP and serotonin were maintained despite ischemia-reperfusion. Endothelium-independent responses to sodium nitroprusside were unaltered in arterioles and venules. Either captopril or enalaprilat restored ADP and A23187 arteriolar responses to control levels and increased bradykinin responses above control levels.. Brief ischemia followed by reperfusion induces arteriolar microvascular endothelial dysfunction, while venular endothelial function is preserved in this porcine model. ACE inhibition enhances coronary blood flow at the time of reperfusion and can prevent impairment of endothelium-dependent arteriolar responses. However, ACE inhibition does not enhance ventricular segmental shortening acutely despite improved microvascular endothelial function and augmented postischemic coronary blood flow in this model of ischemia-reperfusion.

Topics: Adenosine Diphosphate; Angiotensin-Converting Enzyme Inhibitors; Animals; Calcimycin; Captopril; Coronary Vessels; Enalaprilat; Endothelium, Vascular; Female; Hemodynamics; Ionophores; Male; Microcirculation; Reperfusion Injury; Swine