p53 protein and its messenger ribonucleic acid in human adrenal tumors

The role of p53 tumor suppressor gene in the pathomechanism of adrenal tumors was investigated by measuring p53 protein and its messenger ribonucleic acid (mRNA) in 12 normal human adrenals as well as in 56 adrenal tumors (7 aldosterone-producing adenomas, 5 adrenocortical adenomas causing Cushing's syndrome, 19 non-hyperfunctioning adrenocortical adenomas, 5 adrenocortical carcinomas, 12 pheochromocytomas, 3 myelolipomas, 4 ganglioneuromas and 1 hemangioma). The p53 protein concentration was significantly increased in aldosterone-producing adenomas (394+/-36 pg/mg cytosolic protein, mean+/-SE, vs 266+/-18 in normal human adrenals), whereas the concentration of this protein in Cushing's adenomas, non-hyperfunctioning adrenocortical adenomas, pheochromocytomas, and in all but one adrenocortical carcinomas was similar to that measured in normal human adrenal tissues. One adrenocortical carcinoma tissue showed very high p53 protein content (3000 pg/mg cytosolic protein). By contrast, myelolipomas (23+/-20) ganglioneuromas (43+/-15) and a hemangioma (11 pg/mg cytosolic protein) had very low p53 protein content. Northern blot analysis revealed the presence of p53 mRNA in each adrenal tissue examined with highest levels in aldosterone-producing and Cushing's adenomas. It is possible that the differences in p53 protein and/or mRNA contents reflect corresponding differences in the pathogenetic importance of p53 alterations in these types of adrenal tumors.

Effect of recipients' peri-operative parameters on the outcome of kidney transplantation

In this prospectively collected data base multifactorial study, the influence of the peri-operative recipients' parameters on the transplanted kidney function were examined. One hundred and twenty-one patients who underwent first cadaver kidney transplantation in our unit were involved and were followed up for another 2 yr. The recipients were divided into three groups. Group I, patients with non-functioning grafts, group II, with delayed graft function, and group III, with good graft function. All routinely measured parameters were involved in the examination. The pre-operative haematocrit level differed significantly among the three groups. Significant intra-operative differences were found among the three groups in mean arterial pressure, (group I: 81 +/- 31 mmHg, group II: 90 +/- 24 mmHg, vs. group III: 108 +/- 26 mmHg, p < 0.01) at 5 min before revascularisation. The patients who had better post-operative kidney function, had lower pre-operative haematocrit level, and higher blood pressure in the different phase of operation, than those who had post-operative kidney function problems. The second warm ischaemic time in Group III was significantly shorter than in group I. (Group I: 51.5 min vs. group II: 47 min, vs. group III: 46.3 min, p < 0.001). Rejection rate was higher during the first 5 post-operative days in patients with non-functioning grafts. (Group I: 53% and group II: 24% vs. group III: 12% p < 0.001). The other examined parameters had not differed significantly among the three groups. The kidney function differences observed in the early (first 5 d) post-operative period, remained similar at the end of the next 2 yr. According to our results the peri-operative fluid-balance is one of the most important factors which may influence the success of the kidney transplantation.

Differential response of basal and tetrahydrobiopterin-stimulated activities of placental type III nitric oxide synthase to sodium dodecyl sulphate: relation to dimeric structure

The major enzyme isoform that synthesizes nitric oxide (NO) in first trimester human placentae is endothelial or type III NO-synthase (NOS III) which exhibits high specific activity in the microsomal fraction. In the present study, we investigated the possible protective and enzyme-stabilizing role of tetrahydropterin (BH4). The anionic detergent, sodium dodecyl sulphate (SDS) and thermal stress (freeze-thaw) were used as non-specific 'subunit-dissociating' agents, and alterations in enzyme activity and subunit structure were investigated. SDS (> or =0.05% w/v) resulted in significant inhibition both of basal and BH4-stimulated activities of NOS III, but the latter responded more sensitively. Preincubation of microsomes with SDS (> or =0.1%, w/v), followed by incubation in an SDS-depleted reaction mixture led to an inhibition of BH4-stimulated enzyme activity, while no change in the basal activity was noted. This indicated that the SDS effect is only fully reversible in the case of basal activity. Considering that basal activity is due to the presence of endogenous BH4 tightly bound to the enzyme, this differential sensitivity of basal and BH4-stimulated enzyme activities to SDS may be related to a putative differential protective effect of BH4 on the two subunits of the NOS III dimer. Western blot analysis revealed that the SDS-induced inhibition of enzyme activity could not be ascribed to disruption of the dimeric structure. This finding confirms the view that SDS may affect NOS III activity without necessarily deteriorating quaternary protein structure. Nevertheless, BH4 is essential in maintaining dimeric structure under denaturing conditions, e.g. SDS treatment and freezing/thawing; it is even able to reverse the dissociation caused by SDS. A model describing the interaction between BH4 and NOS III, and its implications on the physiology and pathology of the human placenta, is discussed.

[Importance of endocrine imaging methods in multiple endocrine neoplasia type 2A proved by mutation analysis]

Multiple endocrine neoplasias are rare, inherited disorders. The authors describe a case history of a patient with multiple endocrine neoplasia type 2A, who presented with unusual clinical manifestations. The diagnosis of phaeochromocytoma, which was the first manifestation of the disorder, was greatly facilitated with radiologic imaging methods. The authors review, on the basis of recent data from the literature, the importance of radiologic methods, which improved due to methodological advance. Finally, the authors emphasize the importance of follow-up for early diagnosis.

Role of endothelin-1 in diabetes mellitus

Endothelin-1 is mainly synthesized by the vascular endothelial cells and acts on the vascular smooth muscle. Because of its vasoconstrictor and mitogenic effects it plays a role in the development of vascular diseases. In diabetes mellitus atherosclerosis is accelerated. The authors summarize the available data of the role of endothelin-1 in Type 1 and Type 2 diabetes mellitus and the development of diabetic complication.

Sterically inhomogenous viscoelastic behavior of human saccular cerebral aneurysms

To clarify the mechanism leading to the development and rupture of intracranial aneurysms, tensile strength and viscoelastic parameters of 22 human saccular aneurysms were investigated. Meridional and circumferential strips from the thin and the thick part of the aneurysm sack and 18 control strips from the basilar artery of 8 patients with pathologies not affecting the cerebral arterial system were studied. The length of the strips was increased in 200- microm steps, while distending force was recorded. Tensile strength and viscoelastic parameters were computed. In both directions, tensile strength of thick strips was significantly lower than that of controls. In the meridional direction, tensile strength of thin strips was significantly larger than that of thick ones (14.5 +/- 4.1 x 10(6) vs. 7.5 +/- 2.0 x 10(6) dyn/cm2, p < 0.05). In the circumferential direction, thin strips tore at lower strain values than thick ones (29 +/- 4 vs. 55 +/- 16%, p < 0.05). Viscoelastic parameters changed in parallel. In circumferential direction, values of thick and thin strips were significantly lower than those of controls. In the meridional direction, values of thin strips were significantly higher than those of the thick ones. These observations show that characteristic mechanical deterioration and steric inhomogeneities accompany the loss of smooth muscle cells and the derangement of connective tissue elements in the wall of intracranial aneurysms, which may explain certain steps in their initiation, enlargement and rupture.

[Endoscopic anatomy of the tympanic cavity]

Development of modern diagnostic procedure requires inframacroscopic description of tympanic cavity. This description has to suit the special requirements of diagnostic endoscopy, too. The authors made an attempt to describe clinical anatomy of the tympanic cavity. For endoscopic investigation transtympanic, transtubal and transmastoidal approaches were used, out of which the transmastoidal has the least clinical importance. Using the transtympanic approach, detailed anatomical description of the medial wall, the auditory ossicles and the stapedius muscle can be given. Using the transtubal approach, the epitympanic region, stapedius and tensor tympani muscle and two major nerves, chorda tympani and tympanic nerve can be also investigated. Using transmastoidal approach, auditory ossicles were seen, but it was possible to identify lateral part of epitympanic recess, as well.

Coexpression of p53 and tissue transglutaminase genes in human normal and pathologic adrenal tissues

The presence of p53 and tissue transglutaminase (tTG) gene expressions was investigated in human normal and pathologic adrenal tissues with two aims (1) to determine the tissue content of p53 protein, its messenger ribonucleic acid (mRNA) and, especially, tTG mRNA which has not been previously reported and (2) to study possible differences in the coexpression of p53 and tTG in various adrenal disorders. Using Northern blot analysis, p53 and tTG mRNAs were detected in each adrenal tissue examined including 5 normal human adrenals, 6 aldosterone-producing adenomas, 3 Cushing's adenomas, 1 primary nodular adrenocortical hyperplasia causing Cushing's syndrome in an infant, 12 non-hyperfunctioning adrenocortical adenomas, and 4 adrenocortical carcinomas. The results showed a significant positive correlation between these two mRNAs in all adrenal tissues except adrenocortical carcinomas. Compared to normal adrenals, high p53 mRNA levels were observed in aldosterone-producing and Cushing's adenomas and, most markedly, in a tissue from a primary nodular adrenocortical hyperplasia. Also, Cushing's adenomas had significantly higher tTG mRNA contents. Immunohistochemistry for wild-type and mutant p53 protein showed numerous p53 positive cells with a strong nuclear staining in a tissue from a primary nodular adrenocortical hyperplasia, whereas the p53 positive cells were absent, except those with a faint nuclear staining, in all other adrenal tissues. However, all adrenal tissues showed detectable p53 contents by the more sensitive method of luminometric immunoassay (LIA). Using this method, aldosterone-producing adenomas exhibited significantly higher p53 contents than normal adrenal tissues. These observations may support potentially important roles for p53 and tTG in adrenal pathophysiology, especially in mechanisms which influence the evolution and/or progression of aldosterone-producing and Cushing's adenomas and, most probably, hyperplasias.

Neurofibromatosis type 1 with pregnancy-associated renovascular hypertension and the syndrome of hemolysis, elevated liver enzymes, and low platelets

The authors detected a case of neurofibromatosis type 1 complicated with preeclampsia and the syndrome of hemolysis, elevated liver enzymes, and low platelets, which developed during pregnancy. When the cause of the patient's hypertension was investigated after birth, renal stenosis of the right artery was detected, which was then successfully treated with percutaneous transluminal angioplasty.

Role of endothelin-1 in diabetes mellitus

Endothelin-1 is mainly synthesized by the vascular endothelial cells and acts on the vascular smooth muscle. Because of its vasoconstrictor and mitogenic effects it plays a role in the development of vascular diseases. In diabetes mellitus atherosclerosis is accelerated. The authors summarize the available data of the role of endothelin-1 in Type 1 and Type 2 diabetes mellitus and the development of diabetic complication.

Interactions between ouabain, atrial natriuretic peptide, angiotensin-II and potassium: effects on rat zona glomerulosa aldosterone production

The effects of ouabain, atrial natriuretic peptide, angiotensin-II and potassium on aldosterone production by collagenase dispersed rat zona glomerulosa cells were studied. A-II and 10(-4) M ouabain-induced increases in aldosterone production was inhibited by 10(-9) M ANP at all potassium concentrations examined. 10(-4) M ouabain inhibited the A-II induced increase in aldosterone production at all potassium concentrations. The degree of this inhibition was smaller at higher potassium levels. Ouabain enhanced the inhibitory effect of ANP on A-II-induced aldosterone synthesis at all potassium concentrations. Interactions between A-II, ANP, ouabain and potassium may be of physiological significance in the regulation of aldosterone secretion.

Endothelin does not interact with angiotensin II in the coronary vascular bed of anesthetized dogs

We postulated that individually subthreshold circulating levels of angiotension II (Ang II) and endothelin-1 (ET-1) might induce fulminant coronary vasoconstriction when both are present. In 16 pentobarbital-anesthetized, open-chest mongrel dogs, blood pressure, heart rate, and standard ECG were registered continuously. Coronary blood flow (CBF) was measured in the left anterior descending coronary artery (LAD) by an electromagnetic flow probe. Drugs were administered into the LAD via an indwelling catheter. Bolus injections of Ang II (7.8 x 10(-13) to 3.9 x 10(-11) M) and ET-1 (10(-12) to 10(-9) M) induced a dose-dependent decrease in CBF (delta CBFmax -82 +/- 10% for Ang II and -91 +/- 8% for ET-1). Simultaneous Ang II and ET-1 boluses had slightly smaller effects on CBF than the calculated additive figure. Five-minute infusions of Ang II (10(-12) to 10(-10) M/min) and ET-1 (5 x 10(-12) to 2 x 10(-10) M/min) induced a slight decrease in CBF (delta CBFmax -12 +/- 9% for Ang II and -19 +/- 9% for ET). Background ET-1 or Ang II infusions did not alter the dose-response curve of the other drug. Simultaneous Ang II and ET-1 infusions at different rates (10(-12) to 10(-10) M/min for Ang II and 5 x 10(-12) to 2 x 10(-10) M/min for ET-1) over 5 min had similar effects on CBF as the calculated additive figure (delta CBFmax -35 +/- 17% for the joint administration of the highest doses). We conclude that after simultaneous administration into the dog coronary artery, Ang II and ET-1 do not interact sufficiently to induce fulminant vasoconstriction.

Potential pathophysiologic role of endothelin-1 in canine pericardial fluid

Recently, extremely high levels of endothelin-1 (ET-1) were detected in the pericardial fluid of patients undergoing cardiac surgery. This study was designed to assess the pathophysiologic importance of this finding by infusing ET-1 into the closed pericardial sac of anesthetized dogs. Systemic arterial blood pressure, heart rate, and standard ECG were recorded. Intrapericardial infusion of ET-1 (11 and 33 pmol/kg/min; n = 4/4) for 40 min induced ventricular arrhythmias in all instances. The lower dose of ET-1 induced a substantial number of ventricular extrasystoles, couplets, and triplets. In one instance, ventricular extrasystoles accelerated into nonsustained ventricular tachycardia (VT). In animals receiving the higher dose, nonsustained VTs occurred regularly, whereas sustained VTs were detected in two of four animals. Before the onset of arrhythmias, QT time was significantly prolonged [ET-1 (11 pmol/kg/min) 180 +/- 12 to 198 +/- 10 ms, p < 0.05; ET-1 (33 pmol/kg/min) 192 +/- 15 to 233 +/- 13 ms, p < 0.01]. Hemodynamic variables did not change significantly before the onset of ventricular arrhythmias. Our results show that administration of exogenous ET-1 into the pericardial space induces ventricular arrhythmias associated with prolongation of QT time.

Verapamil reduces the arrhythmogenic effect of endothelin

In a previous study we established that endothelin-1 (ET-1) can induce characteristic ventricular tachycardias (VT) with significant prolongation of QT and QTc time. In this investigation we studied the role of CA2+ channels in the pro-arrhythmic effects of ET-1. In 24 anesthetized, open-chest mongrel dogs, ET-1 was administered into the left anterior descending coronary artery at a comparatively low dose (60 pmol/min) for 30 min. Twelve dogs received the Ca(2+)-channel blocker verapamil (0.4 mg/kg) before ET-1 application. The following parameters were recorded continuously over the infusion period: systemic arterial blood pressure, coronary blood flow, surface ECG leads, epicardial atrial and ventricular electrograms, and right and left ventricular endocardial monophasic action potentials (MAP). Electrophysiologic studies were performed by programmed electrical stimulation of the heart. Blockade of myocardial Ca2+ channels attenuated the arrhythmogenic action of ET-1. After verapamil administration to ET-1-treated dogs, sustained VT did not appear and ventricular fibrillation (VF) developed only in two dogs. In the control group serious and sustained VT and VF developed in nine animals. It is noteworthy that verapamil did not prevent ET-1-induced prolongation of QT time. The results appear to prove that myocardial Ca2+ channels are involved in the proarrhythmic effect of ET-1.

Mechanism of endothelin-induced malignant ventricular arrhythmias in dogs

The development of ventricular tachyarrhythmias caused by low-dose intracoronary infusion of endothelin-1 (ET-1) has recently been observed in dogs. The aim of the present study was to investigate the pathomechanism of ET-1-induced ventricular arrhythmias in 32 anesthetized, open-chest mongrel dogs in group A (n = 14) without, in group B (n = 14), and in group C (n = 4 control) with atrioventricular node ablation. The coronary blood flow (CBF) was measured in the left anterior descending (LAD) coronary artery by an electromagnetic flowmeter. Standard ECG, atrial and ventricular electrograms, and in groups B and C endocardial and epicardial monophasic action potentials (MAPs) were recorded. ET-1 was administered into the LAD at a low dose (30-60 pmol/min). At the time of the appearance of premature beats, CBF was only slightly decreased. The effective ventricular refractory period did not change significantly. Onset of spontaneous polymorphic and monomorphic sustained ventricular tachycardia (sVT) was observed in five dogs without bradycardia and in nine dogs with bradycardia. VTs in dogs with complete AV block were longer and slower. In most of the cases, ventricular fibrillation occurred. ET-1 treatment resulted in a significant increase in MAP 90% duration (255 +/- 9 vs. 290 +/- 8 ms endocardial, 244 +/- 10 vs. 292 +/- 12 epicardial; p < 0.05) at 70 beats/min ventricular pacing. In eight cases (group B), third-phase early afterdepolarization could be recorded. According to our results, the mechanism of ET-1-induced arrhythmias appears to be based on prolongation of MAP duration and development of afterdepolarizations.

High pericardial fluid levels of endothelin are not caused by altered neutral endopeptidase activity in cardiac patients

We have previously detected in cardiac patients severalfold higher levels of endothelin (ET) in the pericardial fluid (PF) than in the plasma (PL). We postulated that this is due to different activities of neutral endopeptidase (NEP) in the two compartments. With approval of the ethical committee and informed consent by 32 patients (18 men, 14 women, aged 62 +/- 2 years; NYHA II-IV), PF was taken during cardiac surgery. PL samples were obtained on the day of surgery before premedication. ET was measured by radioimmunoassay after extraction (SepPakC18). NEP activity was measured by a microplate-based kinetic enzyme assay over 120 min. PF ET (78 +/- 11 pg/ml) was significantly (p < 0.05) higher than PL ET (3.38 +/- 0.48 pg/ml). The PF/PL ratio was 38 +/- 14, range 7-200. PF ET was inversely related to the NYHA state of the patients, whereas a similar relation was not found with PL ET. PL and PF ET levels did not correlate. In HPLC, the total immunoreactive ET activity co-eluted with the human ET standard. PF NEP activity (2.26 +/- 0.12 U/l) was lower (p < 0.05) than PL NEP (3.62 +/- 0.22 U/I). PL NEP was not different from that of healthy controls (3.28 +/- 0.22 U/L; n = 50). No correlation was found between NEP in either compartment and the NYHA state of the patients. ET concentration and NEP activity did not correlate in PF or PL. We conclude that ET is extremely high in the PF of cardiac patients and that this is not caused by altered NEP activity.

Bradycardia increases the arrhythmogenic effect of endothelin

The effect of permanent bradycardia on the proarrhythmic action of endothelin-1 (ET) was investigated in 24 open-chest anesthetized mongrel dogs. In 12 dogs, permanent bradycardia was induced by radiofrequency ablation of the AV node and the hearts were paced at 70 beats/min. ET (60 pmol/min) was infused into the left anterior descending coronary artery. Blood pressure, coronary blood flow (CBF), and atrial and ventricular epicardial surface ECG were recorded continuously. Polymorphous ventricular tachycardia developed in every dog with permanent bradycardia, and ventricular fibrillation terminated the experiments in 11 cases. Bradycardia prolonged the basal QT but there was no difference in the frequency corrected QTc time between the two groups. ET prolonged the QT time in a similar fashion in both groups. In the control group, six dogs developed sustained ventricular tachycardias and ventricular fibrillation occurred in nine cases. EADP was found in six cases of eight registered. Signs of myocardial ischemia did not accompany the development of arrhythmias. We conclude that permanent bradycardia augments the direct proarrhythmic effect of ET in dogs.

Increased monophasic action potential dispersion in endothelin-1-induced ventricular arrhythmias

The aim of this study was to investigate the changes in monophasic action potentials (MAP) from different sites in the heart and to determine MAP dispersion during endothelin-1 (ET-1) infusion. Standard ECG, left ventricular anterior, right ventricular lateral, right ventricular septal, and right ventricular apical MAPs and intra-arterial blood pressure were monitored in seven anesthetized open-chest mongrel dogs. After radiofrequency atrioventricular node ablation, ventricular pacing (70/min) was performed and intracoronary ET-1 (60 pmol/min) was administered into the left anterior descending coronary artery. Both MAPd90 and MAPd90 dispersion increased significant during ET-1 infusion. The onset of spontaneous monomorphic and polymorphic sustained ventricular tachycardias (sVT) was observed in five dogs (around 40 min), and nonsustained VTs (nsVT) developed in another two dogs. The increases in MAP and MAP dispersion lasted until the appearance of polymorphic nsVTs and sVTs, but at the time of these VTs this difference decreased. At the termination of the experiments, ventricular fibrillation occurred in six cases. In four cases third-phase early afterdepolarizations were recorded. Our results suggest that increased MAP dispersion and development of EAD contribute to the arrhythmogenic action of ET-1, and these phenomena might explain the pathogenesis of a wide variety of ventricular arrhythmias with different morphology observed in this study.

Endothelin-converting enzyme-1 mRNA expression in human cardiovascular disease

Endothelin-converting enzyme-1 (ECE-1) plays a substantial role in activation of the endothelin (ET) system by cleaving the precursor, big ET-1, to the active peptide ET-1. The aim of this study was to investigate whether ECE-1 mRNA expression is modified in human cardiovascular disease. ECE-1 expression was related to echocardiographic data, drug treatment, age, sex, and NYHA heart failure classification. A quantitative PCR assay (qPCR) was established to measure ECE-1 mRNA in these samples. The ECE-1 measurements were normalized over a simultaneously performed GAPDH qPCR. The results indicate a higher ECE-1 expression level in atrial tissue samples of patients who have experienced a myocardial infarction compared with those who did not (ECE-1/GAPDH: 5.81 +/- 0.76 fg/ng; n = 21 vs. 3.20 +/- 0.51 fg/ng; n = 22; p = 0.007). The transverse diameter of the left atrium over 37 mm was associated with a lower ECE-1 expression (ECE-1/GAPDH: 3.11 +/- 0.69 fg/ng; n = 18 vs. 5.12 +/- 0.65 fg/ng; n = 25; p = 0.044). In assessing the drug treatment, decreased ECE-1 expression could be observed in patients who received a beta-blocker (ECE-1/GAPDH: 3.90 +/- 58 fg/ng; n = 31 vs. 5.81 +/- 0.76 fg/ng; n = 12; p = 0.077). These data suggest an involvement of the ET system is cardiovascular disease that may be clinically important.

Characterization of canine pericardial fluid endothelin-1 levels

Recently, extremely high concentrations of endothelin-1 (ET-1) were detected in the pericardial fluid of patients undergoing cardiac surgery. This study was designed to characterize ET-1 levels in plasma and pericardial fluid of dogs. Plasma and pericardial fluid samples were extracted using SepPak C18 cartridges and ET-1 levels were measured by a specific radioimmunoassay. Pericardial fluid ET-1 levels (739 +/- 81 pg/ml; n = 10) were significantly higher than respective plasma levels (22.4 +/- 4.0 pg/ml; p < 0.05). The mean pericardial fluid: plasma ratio of ir-ET-1 concentration was 54.7 +/- 16.8. In HPLC analysis, the total ET-1-like immunoreactivity of pericardial fluid co-eluted with ET-1 standard. In anesthetized dogs (n = 6), disappearance of [125I]ET-1 was sixfold slower in the pericardial space than in plasma. Our results show that high concentrations of ir-ET-1 can be found in canine pericardial fluid. Slow elimination of ET-1 from the pericardial fluid compartment may contribute to high peptide levels.

Regulation of endothelin release from human brain microvessel endothelial cells

After approval by the Local Ethical Committee, brain microvessel endothelial cells from human cadavers were isolated by enzymatic digestion and gradient centrifugation. Basal levels of endothelin-1 (ET) in the supernatant increased over time (3 h, 18.3 +/- 4.3 pg/ml; 6 h, 31.3 +/- 1.1 pg/ml; 24 h, 88.0 +/- 5.7 pg/ml; 48 h, 86.3 +/- 11.2 pg/ml, mean +/- SD). Tumor necrosis factor-alpha (TNF-alpha) (270 U/ml) increased ET concentration dose-dependently: 3 h, 190 +/- 70%; 24 h, 217 +/- 39%; 48 h, 207 +/- 5%; TNF-alpha at 210 U/ml: 3 h, 137%; 24 h, 170%; 48 h, 212% (values are relative changes from control, run in parallel to the stimulated wells). Interleukin-1 alpha (IL-1 alpha) (38.8 U/ml) also increased ET dose-dependently: (3 h, 129%; 24 h, 161%; 48 h, 212%; IL-1 alpha 1.4 U/ml: 3 h, 116%; 24 h, 122%; 48 h, 180%). Lipoprotein (a) (Lp(a)) had a dual effect on ET, increasing ET in the first 3 h but reducing it by the end of the 48-h observation period. This effect was not dose-dependent in the concentration range tested: Lp(a) 450 micrograms/ml; 3 h, 188%; 24 h, 91%; 48 h, 85%; Lp(a) 360 micrograms/ml: 3 h, 180%; 24 h, 94%; 48 h, 52%). Lp(a) reduced the stimulatory effect of cytokines on ET release. Maximal values at 48 h were TNF-alpha 207%, TNF-alpha + Lp(a) 91%, IL-1 alpha 212%, IL-1 alpha + Lp(a) 64%. In HPLC analysis, the total ET-like immunoreactivity co-eluted with the synthetic human ET standard. A cell culture of human brain microvessel endothelial cells was established. TNF-alpha and IL-1 alpha increased ET secretion, whereas Lp(a) had a dual effect. When given together, Lp(a) reduced the effect of cytokines on ETs.

Endothelin converting-enzyme-1 mRNA expression in human cardiovascular disease

Endothelin-1 converting-enzyme (ECE-1) cleaves the precursor, big-endothelin-1, to the active peptide endothelin-1. The aim of this study was to investigate whether ECE-1 mRNA expression is modified in human cardiovascular disease. Tissue samples from the left human atrium were analyzed for ECE-1 expression and related to different clinical parameters. A quantitative PCR assay (qPCR) with competitive and non-competitive standards was established. The ECE-1 measurements were normalized by a GAPDH qPCR. Patients who suffered from a myocardial infarction had elevated ECE-1 levels when compared to controls (5.81+/-0.76 vs. 3.20+/-0.51 fg ECE-1, ng GAPDH, p<0.05). Drug treatment with the beta-blocker metoprolol was associated with a decreased ECE-1 expression level (3.90+/-0.58 vs. 5.81+/-0.76 fg ECE-1, ng GAPDH, p<0.1). We conclude that the expression of ECE-1 is altered in the atrial tissue depending on the physiological status of the heart. This suggests a differential role of ECE-1 in cardiovascular diseases.

Intrapericardial infusion of endothelin-1 induces ventricular arrhythmias in dogs

OBJECTIVES

Recently, extremely high levels of endothelin-1 (ET-1) were detected in the pericardial fluid of patients with heart disease; however, the pathophysiological importance of this finding is not known. The present study was designed to characterize ET-1 levels in canine pericardial fluid and to investigate the effects of local high concentrations of exogenous ET-1 in vivo.

METHODS

In anesthetized, open-chest dogs ET-1 (Groups 1 and 2: 11 and 33 pmol.kg-1.min-1; n = 6 and 6, respectively) or physiological saline (Group 3, n = 5) were infused into the closed pericardial sac for 40 min. In serial pericardial fluid and aortic blood plasma samples, ET-1 levels were measured by radioimmunoassay, and analysed by high-performance liquid chromatography (HPLC). Systemic arterial blood pressure, heart rate, cardiac output (CO), standard ECG and right ventricular endocardial monophasic action potentials (MAPs) were recorded.

RESULTS

Basal pericardial fluid ET-1 levels were significantly higher than respective plasma levels (342 +/- 210 vs. 8.0 +/- 5.2 pmol.l-1, n = 14, P < 0.001. In HPLC analysis pericardial fluid ET-1 was indistinguishable from ET-1(1-21). Infusion of exogenous ET-1 into the pericardial space induced ventricular arrhythmias in all instances, which were associated with 9.7-fold increase in pericardial fluid ET-1 levels. Ventricular tachycardias developed in 9 of 12 animals. The arrhythmogenic effect of ET-1 was more apparent in dogs with the larger dose. Before the onset of arrhythmias, intrapericardial infusion of ET-1 increased QT time (Group 1: 207 +/- 18 to 230 +/- 23 ms, P < 0.01; Group 2: 220 +/- 12 to 277 +/- 17 ms, P < 0.01) and MAP duration at 90% repolarization (at 300 ms cycle length) (Group 1: 192 +/- 9 to 216 +/- 9 ms, P < 0.01; Group 2: 205 +/- 9 to 255 +/- 9 ms, P < 0.001). Hemodynamic variables did not change significantly prior to the onset of ventricular tachyarrhythmias. In Group 3, arrhythmias were not observed and all electrophysiological and hemodynamic parameters remained unchanged.

CONCLUSIONS

Administration of exogenous ET-1 into the pericardial space induces ventricular arrhythmias associated with prolongation of QT time and MAP duration. Whether pericardial fluid ET-1 under pathophysiological conditions can ever reach sufficiently high levels to induce ventricular arrhythmias remains to be elucidated.

Evidence for cAMP-independent mechanisms mediating the effects of adrenomedullin, a new inotropic peptide

BACKGROUND

Adrenomedullin (ADM), a new vasorelaxing and natriuretic peptide, may function as an endogenous regulator of cardiac function, because ADM and its binding sites have been found in the heart. We characterize herein the cardiac effects of ADM as well as the underlying signaling pathways in vitro.

METHODS AND RESULTS

In isolated perfused, paced rat heart preparation, infusion of ADM at concentrations of 0.1 to 1 nmol/L for 30 minutes induced a dose-dependent, gradual increase in developed tension, whereas proadrenomedullin N-20 (PAMP; 10 to 100 nmol/L), a peptide derived from the same gene as ADM, had no effect. The ADM-induced positive inotropic effect was not altered by a calcitonin gene-related peptide (CGRP) receptor antagonist, CGRP8-37, or H-89, a cAMP-dependent protein kinase inhibitor. ADM also failed to stimulate ventricular cAMP content of the perfused hearts. Ryanodine (3 nmol/L), a sarcoplasmic reticulum Ca2+ release channel opener, suppressed the overall ADM-induced positive inotropic effect. Pretreatment with thapsigargin (30 nmol/L), which inhibits sarcoplasmic reticulum Ca2+ ATPase and depletes intracellular Ca2+ stores, attenuated the early increase in developed tension produced by ADM. In addition, inhibition of protein kinase C by staurosporine (10 nmol/L) and blockade of L-type Ca2+ channels by diltiazem (1 micromol/L) significantly decreased the sustained phase of ADM-induced increase in developed tension. Superfusion of atrial myocytes with ADM (1 nmol/L) in isolated left atrial preparations resulted in a marked prolongation of action potential duration between 10 and -50 mV transmembrane voltage, consistent with an increase in L-type Ca2+ channel current during the plateau.

CONCLUSIONS

Our results show that ADM enhances cardiac contractility via cAMP-independent mechanisms including Ca2+ release from intracellular ryanodine- and thapsigargin-sensitive Ca2+ stores, activation of protein kinase C, and Ca2+ influx through L-type Ca2+ channels.