14 research outputs found
Bradykinin mediates cardiac preconditioning at a distance
Preconditioning the heart by brief coronary (CAO) or mesenteric artery
occlusion (MAO) can protect against damage during subsequent prolonged CAO
and reperfusion. The role of bradykinin (BK) in remote cardiac
preconditioning by MAO is investigated by antagonizing the BK B(2)
receptor [Hoechst 140 (HOE-140)] or simulating local BK release by
mesenteric intra-arterial infusion. Anesthetized male Wistar rats (n =
6-8) were treated with HOE-140 or saline before starting the
preconditioning protocol, CAO, MAO, or non-preconditioned control. Infarct
size related to risk area [ratio of infarct area to area at risk (IA/AR)]
was determined after 3 h of reperfusion following a 60-min CAO. IA/AR was
62 +/- 5% in controls and not affected by HOE-140 (58 +/- 6%). CAO as well
as MAO significantly protected the heart (IA/AR, 37 +/- 3 and 35 +/- 5%),
which was prevented by HOE-140 (IA/AR, 71 +/- 6 and 65 +/- 7%,
respectively). Brief intramesenteric BK infusion mimicked MAO (IA/AR, 26
+/- 3%). Pretreatment with hexamethonium could abolish this protection
(IA/AR, 67 +/- 4%). These data indicate an important role for BK in remote
preconditioning by MAO. Results support the hypothesis that remote
preconditioning acts through sensory nerve stimulation in the ischemic
organ
Sensitivity to ischemia of chronically infarcted rat hearts; effects of long-term captopril treatment
Different pharmacological responses of atrium and ventricle: Studies with human cardiac tissue
It has been recently reported that 5-hydroxytryptamine (5-HT) increases force of contraction in atrial tissue but not in ventricular tissue. In the present study with trabeculae obtained from non-diseased human hearts, we investigated whether this difference in the contractile response is specific for 5-HT or is also observed for other substances: calcitonin gene-related peptide (CGRP), angiotensin II, adenosine, somatostatin and acetyllcholine. CGRP (10β9 to 10β7 M) and angiotensin II (10β9 to 10β5 M) caused concentration-dependent increases in force of contraction in atrial trabeculae (up to36 Β± 8%and42 Β± 8% of the response to 10β5 M noradrenaline, respectively). Similar to 5-HT, no effects were observed with CGRP and angiotensin II in ventricular trabeculae. Adenosine (10β8 to 10β5 M) and somatostatin (10β8 to 10β6 M) caused concentration-dependent negative inotropic effects on baseline atrial contractility (β54 Β± 17%andβ51 Β± 25%, respectively, but no response was found on baseline ventricular contractility. Adenosine, but not somatostatin, reduced force of contraction after pre-stimulation with 10β5 M noradrenaline in atrial tissue and, to a lesser extent, in ventricular tissue. Acethlcholine exhibited a biphasic concentration-response curve in the atrial tissue, consisting of an initial negative inotropic response (10β9 to 10β7 M, from 120 Β± 41mg at baseline to48 Β± 16mg at 10 β7 M, fol lowed by a positive inotropic response (10β6 to 10β3 M, from 48 Β± 16 mg at 10β7 M to77 Β± 55mg). On the baseline ventricular for foce of contraction, acetylcholine (10β9 to 10β4 M) induced only a positive inotropic effect, starting at 10β9 M (from 252 Β± 65mg at baseline to353 Β± 71mg at 10β4M). After pre-stimulation with 10β5 M noradrenaline, acethylcholine reduced force of contraction in both tissue at 10β3 M(atrium: β14 Β± 4%,ventricle: β61 Β± 5%). The data indicate that, in atrial tissue, force of contraction can be affected by either postive or negative inotropic agents. However, in ventricular tissue only positive inotropic effects could be detected. Since atrial and ventricular tissues display different responses to the above biogenic substances, a different mechnism of regulation of contractility seems feasible
Characterization of the positive and negative inotropic effects of acetylcholine in the human myocardium
In the human isolated myocardium, acetylcholine (10β9 to 10β3 M) elicited a biphasic inotropic effect (a decrease in the lower and an increase in the higher concentration range) in atrial and a positive inotropic effect in ventricular trabeculae. However, under conditions of raised contractility achieved by exposure to noradrenaline (10β5 M), only negative inotropic effects were observed in both atria and ventricles. Atropine (10β6 M), but not propranolol (10β6 M), antagonized both positive and negative inotropic effects of acetylcholine, thus showing that the responses were mediated by muscarinic acetylcholine receptors. The use of subtype selective muscarinic receptor antagonists (10β7 to 10β5 M), pirenzepine (M1 > M3 > M2), AF-DX 116 (11-({2-[(diethylamino)-methyl]-1-piperidyl}acetyl)-5,11-dihydro-6H-pyridol[2,3-b][1,4]benzodiazepine-6-one base; M2 > M1 > M and HHSiD (p-fluorohexahydro-siladifenidol hydrochloride; M3 β₯ M1 βͺ’ M2) revealed that the negative inotropic effect of acetylcholine in atrial as well as the positive inotropic effect in ventricular trabeculae were best antagonized by AF-DX 116 and not by pirenzepine, suggesting the involvement of the muscarinic M2 receptor subtype, possibly linked to different second messenger systems. On the other hand, the positive inotropic effect of acetylcholine (10β6 to 10β3 M) in the atrial tissue, observed only in preparation with depressed contractility, was not effectively antagonized by either AF-DX 116 or HHSiD, but was significantly reduced by pirenzepine. Furthermore, the selective muscarinic M1 receptor agonist McN-A-343 (4-(m-chlorophenylcarbamoyloxy)-2-butynyltrimethyl ammonium chloride; 10β9 to 10β3 M), which failed to significantly change the baseline contractility in either atrial or ventricular trabeculae, produced a positive inotropic effect in atrial preparations when contractility had been depressed by prior treatment with acetylcholine (10β9 to 10β7 M). This effect of McN-A-343 was effectively antagonized by pirenzepine (10β5 M). These data show that, besides the muscarinic M2 receptor mediating both negative (atria) and positive (ventricle) inotropic effects, muscarinic M1 receptors, capable of reversing depressed atrial contractility, are present in the human heart
Carotid blood flow distribution, haemodynamics and inotropic responses following calcitonin gene-related peptide in the pig
The sensory neuropeptide, calcitonin gene-related peptide (Ξ±-CGRP), has been implicated in the pathogenesis of migraine headache. The present study aimed to evaluate the effects of intracarotid infusions of human Ξ±-CGRP (10, 30 and 100 pmol/kg Β· min; n = 8), as compared to that of saline (4 times; n = 8) on haemodynamics and blood flow distribution within the carotid circulation of the anaesthetized pig, using the radioactive microsphere method. Furthermore, the effects of antimigraine drugs, dihydroergotamine (100 ΞΌg/kg i.v; n = 4) or sumatriptan (300 ΞΌg/kg i.v.; n = 4), on these parameters were studied in the presence of the infusion of the highest concentration of human Ξ±-CGRP. Additionally, putative positive inotropic responses to human Ξ±-CGRP (10β9β10β7 M) were investigated in porcine isolated atrial and ventricular trabeculae. Human Ξ±-CGRP increased carotid artery blood flow and conductance dose-dependently, together with an enhancement in vascular pulsations. These effects were associated with a fall in systemic blood pressure with concomitant increases in heart rate and cardiac output. The increase in carotid blood flow was reflected by an increase in total capillary blood flow, predominantly to extracerebral tissues including the dura, whereas blood flow through arteriovenous anastomoses remained stable. Both dihydroerogtamine and sumatriptan reduced carotid blood flow and its capillary fraction without affecting systemic vascular conductance. In tissues, these drugs reversed blood flow increases due to human Ξ±-CGRP in most extracerebral tissues, but failed to reduce dural blood flow. In porcine isolated atrial and ventricular trabeculae, noradrenaline (10β8β10β5 M) increased force of contraction in a concentration-dependent manner. In contrast, human Ξ±-CGRP (10β9β10β7 M) failed to increase force of contraction in atrial trabeculae (n = 6) and exerted only a moderate concentration-dependent positive inotropic effect in ventricular trabeculae (βΌ 25% of the response to 10β5 M noradrenaline, n = 10). These data indicate that human Ξ±-CGRP caused arteriolar dilatation together with a fall in blood pressure in the pig. The tachycardia may be reflex-mediated, but the peptide also exerts a moderate positive inotropic action on ventricular trabeculae. The fall in systemic arterial blood pressure and the marked increase in capillary blood flow most likely prevented the opening of arteriovenous anastomoses. Furthermore, the antimigraine drugs, dihydroergotamine and sumatriptan, were able to reverse blood flow changes induced by human Ξ±-CGRP in the porcine carotid circulation
AT(2) receptor-mediated vasodilation in the heart: effect of myocardial infarction
To investigate the functional consequences of postinfarct cardiac
angiotensin (ANG) type 2 (AT(2)) receptor upregulation, rats underwent
coronary artery ligation or sham operation and were infused with ANG II
3-4 wk later, when scar formation is complete. ANG II increased mean
arterial pressure (MAP) more modestly in infarcted animals than in sham
animals. The AT(1) receptor antagonist ir
Chronic aspirin treatment affects collagen deposition in non-infarcted myocardium during remodeling after coronary artery ligation in the rat
Low-dose aspirin (acetylsalicylic acid; ASA), inhibiting platelet thromboxane production in favor of endothelium formation of prostaglandins, is successfully used as primary or secondary prophylaxis against myocardial infarction. Although prognosis may be improved, effects of long-term ASA treatment on wound healing and cardiac remodeling are not well understood. The aim of the present study was to mimic the clinical situation by inducing myocardial infarction in low-dose ASA (25 mg/kg/day, i.p.) pretreated rats, and to determine effects on plasma eicosanoid levels, cardiac hypertrophy and collagen deposition, and left ventricular function during continued ASA treatment. The effects of this dose were verified to selectively inhibit platelet thromboxane production, and lower plasma levels of thromboxane, but did not affect plasma levels of prostacyclin and prostaglandin E2during the acute inflammatory stage following myocardial infarction. As measured by heart dry weight/body weight, cardiac hypertrophy was not affected by ASA treatment. However, interstitial fibrosis in the spared myocardium as well as perivascular fibrosis, associated with infarction-induced cardiac remodeling, were affected by ASA treatment. Replacement fibrosis in the infarct itself, considered as representing wound healing, was not significantly influenced by ASA treatment. Wall thinning following infarction was not aggravated, nor did treatment influence left ventricular cavity diameter in a relaxed state. Results fromin vitroleft ventricular function measurements showed no effects on left ventricular peak velocity of contraction or relaxation after ASA treatment. In conclusion, although low-dose ASA may not be expected to have anti-inflammatory action, it did influence post-infarct cardiac remodeling by affecting interstitial and perivascular fibrosis. ASA treatment did not have effects onin vitroleft ventricular dysfunction
Determinants of coronary reserve in rats subjected to coronary artery ligation or aortic banding
Non-Bone Marrow Origin of Neointimal Smooth Muscle Cells in Experimental In-Stent Restenosis in Rats
BackgroundRenal failure aggravates pathological cardiac remodelling induced by myocardial infarction (MI). Cardiac remodelling is associated with telomere shortening, a marker for biological ageing. We investigated whether mild and severe renal failure shorten cardiac telomeres and excessively shorten telomeres after MI.MethodsRats were subjected to sham, unilateral (UNX) or 5/6th nephrectomy (5/6NX) to induce none, mild or severe renal failure. MI was induced by left coronary artery ligation. Renal function parameters and blood pressure were measured. DNA was isolated from non-infarcted cardiac tissue. Telomere length was assessed by quantitative polymerase chain reaction (PCR).ResultsProteinuria was unchanged in UNX and MI compared with control, but strongly increased in 5/6NX, UNX+MI and 5/6NX+MI. Serum creatinine levels were increased fourfold in 5/6NX and tenfold in 5/6NX+MI. 5/6NX and groups with both renal failure and MI showed an approximate 20% reduction of telomere length, similar to the MI group. No excess telomere shortening was observed in hearts from rats with renal ablation after MI.ConclusionSevere renal failure, but not mild renal failure, leads to shortening of cardiac telomeres to a similar extent as found after MI. Renal failure did not induce excessive telomere shortening after MI. (Neth Heart J 2009;17:190β4.
Non-Bone Marrow Origin of Neointimal Smooth Muscle Cells in Experimental In-Stent Restenosis in Rats
BackgroundRenal failure aggravates pathological cardiac remodelling induced by myocardial infarction (MI). Cardiac remodelling is associated with telomere shortening, a marker for biological ageing. We investigated whether mild and severe renal failure shorten cardiac telomeres and excessively shorten telomeres after MI.MethodsRats were subjected to sham, unilateral (UNX) or 5/6th nephrectomy (5/6NX) to induce none, mild or severe renal failure. MI was induced by left coronary artery ligation. Renal function parameters and blood pressure were measured. DNA was isolated from non-infarcted cardiac tissue. Telomere length was assessed by quantitative polymerase chain reaction (PCR).ResultsProteinuria was unchanged in UNX and MI compared with control, but strongly increased in 5/6NX, UNX+MI and 5/6NX+MI. Serum creatinine levels were increased fourfold in 5/6NX and tenfold in 5/6NX+MI. 5/6NX and groups with both renal failure and MI showed an approximate 20% reduction of telomere length, similar to the MI group. No excess telomere shortening was observed in hearts from rats with renal ablation after MI.ConclusionSevere renal failure, but not mild renal failure, leads to shortening of cardiac telomeres to a similar extent as found after MI. Renal failure did not induce excessive telomere shortening after MI. (Neth Heart J 2009;17:190β4.