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Notes: Although prognosis of dilated cardiomyopathy (DCM) has improved due to advances in diagnosis and therapy, still too many sudden cardiac deaths occur in DCM. Spontaneous ventricular ectopy is a very common finding in patients with DCM, but the prognostic significance of Holter monitoring remains controversial. Other noninvasive methods, e.g., late potentials and QT dispersion, have not yet contributed to the evaluation of prognosis for arrhythmogenic events in DCM. Programmed ventricular stimulation has been repeatedly used to stratify long-term prognosis, yet satisfactory data are still missing as many deaths occur in patients without inducible arrhythmias. Several prognostic studies are still in progess, and preliminary data for the use of ICDs already appear to be promising. In patients with poor left ventricular function and ICDs in situ, prognosis is determined by progression of heart failure. Heart transplantation may be the ultimate therapeutic instrument for end-stage heart failure patients. For patients with advanced DCM and increased risk for malignant arrhythmias who are unsuitable for orthotopic heart transplantation, the combined therapy with an ICD and dynamic cardiomyoplasty may be an alternative treatment.

Notes: Abstract The extent and time-course of changes in lung volumes, ventilatory efficiency at rest and during exercise, and respiratory muscle function and their influence on exercise limitation in congestive heart failure (CHF) are unclear. It is unknown whether respiratory muscle function may predict changes in exercise limitation or may be impaired in patients with poor outcome. 145 male patients (54±1 years) suffering from CHF (NYHA class I–III, mean 2.3±0.1), with a LVEF of 23±1 %, and a mean peak O2 uptake (VO2peak) 15.0±:0.5 mL×min−1×kg−1, were studied. They were grouped in Weber functional classes A to D according to their VO2peak. Significant increases in ventilatory equivalents for O2 and CO2 (VE/VCO2peak) and in dead space ventilation at rest and during exercise were found with increasing exercise limitation. Moreover, there was a correlation of static and dynamic lung volumes (inspiratory vital capacity, IVC, r = 0.43, P 〈 0.01), as well as of maximal inspiratory pressure (MIP; r = 0.46, P 〈 0.01) with VO2peak. Patients who died (n = 26) or were heart transplanted (n = 20) during a follow-up (mean 800 ± 10 days) had a reduced MIP (6.4 ± 0.4 kPa) as compared with survivors (n = 82; 9.3±0.7 kPa, P 〈 0.01). In a subgroup of 33 patients re-evaluated after six months, individual changes in IVC and VE/VCO2peak, but not in MIP, correlated to changes in VO2peak (r = 0.69 and r = 0.72 respectively; P 〈 0.01). In CHF, exercise limitation is associated with reversible lung restriction and inefficient ventilation at rest and during exercise. Patientss with severe CHF have a significant reduction in MIP, a finding that is associated with poor outcome.

Notes: Summary The role of calcium, calcium influx through calcium channels, and activation of protein kinase C for the nicotine-induced release of noradrenaline and of the sympathetic co-transmitter neuropeptide Y (NPY) was investigated in the guinea-pig isolated perfused heart. In the coronary venous overflow noradrenaline and NPY were determined by high-pressure liquid chromatography and radioimmunoassay, respectively. In the presence of extracellular calcium (1.85 mmol/l) nicotine (1–100 μmol/l) evoked a concentration-dependent overflow of both transmitters with a molar ratio of approximately 1500 (noradrenaline):1 (NPY). The nicotine-induced (100 μmol/l) overflow of noradrenaline and NPY was in a linear manner related (r = 0.79 and 0.90, respectively; p 〈 0.05) to the extracellular calcium concentration (0–1.85 mmol/l), and it was prevented by calcium-free perfusion. The L-type calcium channel blocker felodipine (100 nmol/l) did not affect the nicotine-induced (100 μmol/l) transmitter overflow. On the other hand, the neuronal (N-type) calcium channel blockers ω-conotoxin (100 nmol/l) and cadmium chloride (50 μmol/l) reduced the nicotine-induced (100 pmol/l) transmitter overflow to 20% of the control value, suggesting a role of N-type calcium channels in mediating the calcium influx for the nicotine-induced transmitter release. The nicotine-induced (30 μmol/l) overflow of both transmitters was two- to three-fold increased by activation of protein kinase C (phorbol 12-myristate 13-acetate; 100 nmol/l). The transmitter overflow was unaffected by 4α-phorbol 12,13-didecanoate (100 nmol/l), a phorbol ester which does not stimulate protein kinase C. Further supporting a modulatory role of protein kinase C, inhibition of the enzyme by either polymyxin B (100 gmol/I) or by cremophor RH-30 (1μmol/l) almost completely suppressed the overflow of noradrenaline and NPY. The results of the present study indicate that nicotine evokes a concentration-dependent exocytotic co-release of noradrenaline and NPY in the guinea-pig isolated perfused heart which is characterized by its dependence on extracellular calcium, calcium influx through N-type calcium channels and activation of protein kinase C.

Notes: Abstract Neuropeptide Y (NPY) is a sympathetic cotransmitter and a platelet-derived factor which causes vasoconstriction, potentiation of norepinephrine (NE) action, and vascular mitogenic effects. Reciprocally, NE markedly enhances the actions of NPY. We studied vasopressor effects of NPY and sources of peptide release during the development of hypertension in spontaneously hypertensive rats (SHR). Conscious SHR (4 and 16 weeks old) had higher resting plasma levels of NE and epinephrine than age-matched Wistar-Kyoto (WKY) rats, but similar NPY immunoreactivity (NPY-ir) levels in platelet-poor plasmas (PPP). In both strains, NPY-ir levels in PPP were higher in 4-week-old than in older rats. However, at all ages (4–24 weeks) SHR had markedly elevated NPY-ir content in platelet-rich-plasmas than WKY rats, although levels declined with age and hypertension. In the superior mesenteric artery. NPY-ir content (per mg) was significantly higher in 4-week-old but lower in 16-week-old SHR than in WKY rats, suggesting greater sympatho-neural NPY stores and release (leading to depletion) during the development of hypertension. Four-week-old SHR also tended to have higher NPY-ir content in the adrenal medullae and coeliac ganglia but a lower content in the kidney than WKY rats; these differences disappeared with age. Pressor responsiveness to α-agonists and NPY were similar in both strains at 4 weeks. While unchanged by age in WKY rats, adrenergic and NPY-mediated vasopressor responses became augmented in 16- to 24-week-old SHR (compared with WKY rats); this hyperresponsiveness was not completely abolished by ganglionic blockade and not observed with vasopressin. The development of adrenergic hyperresponsiveness in SHR in the face of higher circulating catecholamines suggests a defect in downregulation of α-adrenoceptors. Since we have previously found that NPY can reverse pressor desensitization to NE, we postulate that increased release of platelet and sympatho-neural NPY leads to impaired adrenergic desensitization, whereas adrenergic/NPY interactions tesult in sensitization to NPY in SHR, and thus may contribute to vascular hyperreactivity and hypertrophy.

Notes: Summary The relationship between noradrenaline and neuropeptide Y (NPY) release was investigated in the in situ perfused guinea pig heart with intact sympathetic innervation. For determination of NPY concentrations in the perfusate, a specific radioimmunoassay was employed and further characterized. Electrical stimulation of the left stellate ganglion (4, 8, 12, and 50 Hz; for 10 min) evoked a calcium-dependent and frequency-related overflow of noradrenaline and NPY, which was positively correlated (r = 0.83; p 〈 0.001; n = 25). When two subsequent stimulations (12 Hz; each for 1 min) were performed in the same heart, addition of noradrenaline (10 μM) 5 min prior to the second stimulation reduced NPY overflow by 43 ± 10%. The stimulated release of noradrenaline and NPY was increased by the alpha2-adrenoceptor antagonist yohimbine (1 μM) to 170 ± 10% and 199 ± 26%, and attenuated by the alpha2-adrenoceptor agonist B-HT 920 (1 μM) to 70 ± 9% and 68 ± 9%, respectively. The adenosine analogue cyclohexyladenosine (1 μM) significantly reduced the stimulated overflow of both noradrenaline (to 57 ± 5%) and NPY (to 73 ± 8%). Exogenous NPY (100 nM) attenuated the stimulated overflow of noradrenaline by 30 ± 6%. Uptake1 blockade with desipramine (100 nM) or nisoxetine (100 nM) prior to the second stimulation significantly increased noradrenaline overflow and attenuated that of NPY; the attenuation of the stimulation-evoked overflow of NPY was abolished by yohimbine (1 μM). Our results indicate that electrical stimulation induces a calcium-dependent, exocytotic co-release of noradrenaline and NPY. The co-release of both transmitters is regulated by presynaptic receptors in a parallel manner; furthermore, both transmitters, noradrenaline and possibly NPY, modulate their own release by a presynaptic negative feedback mechanism via presynaptic alpha2-adrenoceptors and NPY-receptors.

Notes: Summary The overflow of neuropeptide Y (NPY; radioimmunoassay), noradrenaline and dihydroxyphenylethylenglycol (DOPEG; high pressure liquid chromatography) from guinea-pig perfused hearts was investigated in relationship to exocytotic and nonexocytotic release mechanisms. Exocytotic release: Electrical stimulation of the left stellate ganglion (12 Hz; 1 min) evoked a calcium-dependent overflow of noradrenaline and NPY, that was accompanied by a minor and prolonged increase in DOPEG overflow. This increase in DOPEG overflow was attenuated by blockade of neuronal amine re-uptake. In the presence of calcium, a closely related co-release of noradrenaline and NPY was also observed during administration of veratridine (10 μM); it was completely prevented by tetrodotoxin (1 μM). Nonexocytotic release: In the absence of extracellular calcium, veratridine (30 μM) induced noradrenaline overflow only when combined with the reserpine-like agent Ro 4-1284 (10 μM). This overflow was accompanied by efflux of DOPEG, but not of NPY. Similarily, tyramine (1–100 μM) induced a calcium-independent concomitant overflow of both noradrenaline and DOPEG, but not of NPY. During anoxic and glucose-free perfusion a predominantly calcium-independent overflow of noradrenaline was observed; only in the presence of extracellular calcium was this overflow accompanied by a minor overflow of NPY. Noradrenaline overflow, induced by veratridine plus Ro 4-1284 (in the absence of calcium), by tyramine, or by anoxia, was suppressed by blockade of neuronal amine re-uptake, and was, therefore, mediated by reversed transmembrane amine transport by the neuronal uptake1 carrier. The results indicate that NPY is co-released with noradrenaline only during calcium-dependent exocytosis. On the other hand, whenever, noradrenaline is released by non-exocytotic (calcium-independent and carrier-mediated) release mechanisms, no substantial NPY overflow is observed. The simultaneous determination of noradrenaline and NPY overflow, therefore, allows a differentiation between exocytotic and nonexocytotic noradrenaline release, and NPY may be utilized as a marker of exocytotic noradrenaline release.

Notes: Summary Ischemia induces a nonexocytotic noradrenaline release in the heart, which leads to high and potentially harmful interstitial noradrenaline concentrations. The effect of beta-adenoceptor antagonists on noradrenaline release in ischemia has been investigated in the present study. DL-Propranolol (1–100 μmol/l) concentration-dependently reduced noradrenaline release during 20 min of global and total ischemia in the perfused rat heart. Other beta-adrenoceptor blocking agents such as atenolol, metoprolol, and timolol (10 μmol/l each), however, did not share this effect. Moreover, both stereoisomers of propranolol were equipotent in suppression of ischemia-induced noradrenaline release, indicating a property of propranolol independent from interaction with beta-adrenoceptors. The well known local anesthetic action of propranolol was not likely to cause its inhibitory effect on ischemia-induced noradrenaline release, as lidocaine (10 μmol/l) did not affect noradrenaline overflow in ischemia. The effect of propranolol was further examined in cyanide intoxication, an experimental model of energy depletion. In this experimental setting the release of dihydroxyphenylethyleneglycol - the major neuronal metabolite of noradrenaline - served as indicator of increased axoplasmic noradrenaline levels which are present during nonexocytotic noradrenaline release. In cyanide intoxication DL-propranolol also reduced noradrenaline overflow but did not affect release of dihydroxyphenylethylene glycol. The latter finding suggests an interaction of propranolol with the neuronal membrane transport of noradrenaline. In ischemia and cyanide intoxication, transport of noradrenaline across the plasma membrane is known to be driven by the noradrenaline carrier (uptake,) working in reverse of its normal direction - from inside to outside. Consequently, inhibitors of the noradrenaline carrier like desipramine were shown to suppress nonexocytotic noradrenaline release in ischemia and cyanide intoxication. In order to test the ability of propranolol to interact with the noradrenaline carrier a model of 3H-noradrenaline uptake was employed in normoxic rat heart. DL-Propranolol concentration-dependently (1–100 μmmol/l) inhibited 3H-noradrenaline uptake, while atenolol and timolol did not interfere with 3H-noradrenaline uptake. In conclusion, the results indicate suppression of noradrenaline release in myocardial ischemia by propranolol. This action of propranolol is independent of its beta-adrenoceptor blocking properties and is rather due to an interaction of propranolol with the neuronal noradrenaline transport mechanism (uptake1).

Notes: Summary The role of the cardiac energy status in the potassium-evoked exocytosis of both noradrenaline and the sympathetic co-transmitter neuropeptide Y (NPY) was investigated in the guinea-pig perfused heart. The transmitter release was stimulated by potassium depolarization (10–80 mmol/l) during normoxic perfusion (pO2 〉 100 mmHg) in the presence of glucose (11 mmol/l) and at various periods (5–40 min) of cardiac energy depletion. Energy depletion was induced either by anoxia (pO2 〈 5 mmHg) or by cyanide intoxication (1 mmol/l), both in combination with glucose-free perfusion. Endogenous noradrenaline and NPY were determined in the coronary venous overflow by high-pressure liquid chromatography combined with electrochemical detection and by radioimmunoassay, respectively. Under normoxic conditions potassium depolarization evoked a co-release of both transmitters [molar ratio 862 (noradrenaline) :1 (NPY)] at a threshold concentration of 40 mmol/l potassium. This transmitter overflow was characterized by its dependence on extracellular calcium and calcium influx through voltage-dependent neuronal calcium channels of the N-type. Cardiac energy depletion was accompanied by an acceleration and an enhancement of the potassium-evoked transmitter overflow. In comparison to normoxia, a 10-fold increased transmitter overflow with a comparable molar ratio [709 noradrenaline :1 (NPY)] was evoked by 40 mmol/l potassium after 10 min of either anoxia or cyanide intoxication. This sensitization to potassium depolarization reached a peak after 10 min of energy depletion and was characterized by a markedly reduced threshold concentration (10 mmol/l potassium). The enhanced sympathetic transmitter overflow in anoxia was suppressed by addition of glucose (11 mmol/l) to the perfusion buffer, suggesting that the sensitization of the overflow of noradrenaline and NPY to potassium depolarization requires a cessation of energy metabolism. The sensitization of the potassium-evoked (20 mmol/l) sympathetic transmitter overflow by energy depletion was further characterized: Consistent with an exocytotic release mechanism, the overflow was calcium-dependent. In contrast to normoxia, however, blockade of neuronal N-type calcium channels by either co-conotoxin (100 nmol/1) or cadmium chloride (50 μmol/l) failed to reduce the potassium-evoked overflow of noradrenaline and NPY. In anoxia blockade of sodium-proton exchange by amiloride (1 mmol/l) or more specifically by ethylisopropylamiloride (1 μmol/l) markedly attenuated the potassium-evoked transmitter overflow. Likewise, suppression of the potassium-evoked overflow of noradrenaline and NPY from the energy-depleted heart was achieved by extracellular acidosis (pH 6.0). In contrast, during normoxia blockade of sodium-proton exchange by either ethylisopropylamiloride (1 μmol/l) or by extracellular acidosis (pH 6.0) did not affect the potassium-evoked (80 mmol/l) transmitter overflow. These findings suggest that the sensitization of sympathetic nerve endings to potassium depolarization, caused by cardiac energy depletion, requires sodium entry into the sympathetic nerve ending via sodium-proton exchange. The results of the present study indicate, that the threshold concentration for the potassium-evoked exocytotic release of noradrenaline and NPY from the guinea-pig isolated perfused heart is intimately coupled to the energy status of cardiac sympathetic nerve fibres. The energy status not only determines the quantity of the transmitters released but also the mode of sodium and calcium entry triggering the depolarization-evoked transmitter overflow. Preliminary findings were reported at the 63rd Scientific Sessions of the American Heart Association, Dallas/USA (Haass et al., 1990b) and at the Annual Meeting of the European Section of the International Society for Heart Research, Leuwen/Belgium (Haass et al. 1991b)