Ilkka Pörsti

Release of nitric oxide by angiotensin‐(1–7) from porcine coronary endothelium: implications for a novel angiotensin receptor

The angiotensin I (AI) metabolite, A(1–7), elicited a concentration‐dependent dilator response (ED50 ≥ 2 μm) in porcine coronary artery rings which was markedly attenuated by the nitric oxide (NO) synthase inhibitor, NG‐nitro‐l‐arginine, and abolished after removal of the endothelium. This effect of the heptapeptide was not mimicked by AII, AIII or A(3–8) at comparable concentrations. The A(1–7)‐induced relaxation was not affected by AT1 or AT2 receptor blockade or cyclo‐oxygenase inhibition, but was attenuated by the B2 receptor antagonist, Hoe 140, and augmented by the angiotensin‐converting enzyme (ACE) inhibitor, quinaprilat. These findings suggest that the relaxation to A(1–7) was mediated by the release of NO from the coronary endothelium through activation of an, as yet unidentified, AT receptor, the occupation of which also seems to stimulate the release of vasoactive kinins. Since A(1–7) accumulates during ACE inhibition, this mechanism may contribute to the coronary dilator effect of ACE inhibitors in vivo.

Bacterial Endotoxin Activity in Human Serum Is Associated With Dyslipidemia, Insulin Resistance, Obesity, and Chronic Inflammation

OBJECTIVE To investigate whether bacterial lipopolysaccharide (LPS) activity in human serum is associated with the components of the metabolic syndrome (MetS) in type 1 diabetic patients with various degrees of kidney disease and patients with IgA glomerulonephritis (IgAGN). RESEARCH DESIGN AND METHODS Serum LPS activity was determined with the Limulus Amoebocyte Lysate chromogenic end point assay in type 1 diabetic patients with a normal albumin excretion rate (n = 587), microalbuminuria (n = 144), macroalbuminuria (n = 173); patients with IgAGN (n = 98); and in nondiabetic control subjects (n = 345). The relationships of the LPS/HDL ratio and MetS-associated variables were evaluated with Pearson correlation. RESULTS The MetS was more prevalent in type 1 diabetic patients (48%) than in patients with IgAGN (15%). Diabetic patients with macroalbuminuria had a significantly higher serum LPS/HDL ratio than patients with IgAGN. In the normoalbuminuric type 1 diabetic group, patients in the highest LPS/HDL quartile were diagnosed as having the MetS three times more frequently than patients in the lowest quartile (69 vs. 22%; P < 0.001). High LPS activity was associated with higher serum triglyceride concentration, earlier onset of diabetes, increased diastolic blood pressure, and elevated urinary excretion of monocyte chemoattractant protein-1. CONCLUSIONS High serum LPS activity is strongly associated with the components of the MetS. Diabetic patients with kidney disease seem to be more susceptible to metabolic endotoxemia than patients with IgAGN. Bacterial endotoxins may thus play an important role in the development of the metabolic and vascular abnormalities commonly seen in obesity and diabetes-related diseases.

Potentiation by ACE inhibitors of the dilator response to bradykinin in the coronary microcirculation : interaction at the receptor level

1 To examine the possibility that angiotensin‐converting enzyme (ACE) inhibitors modulate the action of bradykinin at the receptor level, their effect on the dilator response to bradykinin was studied in the isolated saline‐perfused heart of the rabbit. 2 Continuous infusion of bradykinin (10 nM) elicited a transient decrease in coronary perfusion pressure (CPP) and increased prostacyclin (PGI2) release which returned to baseline values within 30 min. 3 Subsequent co‐infusion of ramiprilat (≥ 10 nM) or moexiprilat, but not of the less potent ACE inhibitor n‐octyl‐ramipril (RA‐octyl), caused another fall in CPP and an increase in PGI2 release, the magnitude and time course of which were almost identical to the first response to bradykinin. No change in CPP or PGI2 release was observed when the ACE inhibitors were administered in the absence of exogenous bradykinin. 4 Infusion of d‐Arg[Hyp3]‐bradykinin (10 nM), a specific B2‐receptor agonist which was significantly more resistant to degradation by ACE than bradykinin, produced virtually identical changes in CPP and PGI2 release when compared to bradykinin. Subsequent co‐infusion of ramiprilat was similarly effective in restoring the fall in CPP and increase in PGI2 release elicited by d‐Arg[Hyp3]‐bradykinin as in the presence of bradykinin. 5 In concentrations which should block the degradation of bradykinin by ACE in the coronary vascular bed, two ACE substrates, hippuryl‐l‐histidyl‐l‐leucine (0.2 mM) and angiotensin I (0.3 μm), were unable to elicit a significant change in CPP or PGI2 release while ramiprilat and another ACE inhibitor, quinaprilat, were still active in the presence of these substrates. 6 To reveal the potential B2‐receptor action of ramiprilat, its effect on the constrictor response to bradykinin was studied in the rabbit isolated jugular vein. Ramiprilat (0.1 μm), but not RA‐octyl (1 μm), potentiated the endothelium‐independent, B2‐receptor‐mediated constrictor response to bradykinin, but not that to the thromboxane‐mimetic U46619 (9,11‐dideoxy‐11α,9α‐epoxymethano‐prostaglandin F2α). Moreover, ramiprilat but not RA‐octyl caused a concentration‐dependent, B2‐receptor antagonist‐sensitive increase in tone when administered alone. 7 These findings suggest that an interaction of ACE inhibitors with the B2‐receptor or its signal transduction pathway rather than an accumulation of bradykinin within the vascular wall is responsible for the restoration of the endothelial response to bradykinin (dilatation, PGI2 release) in the coronary vascular bed of the rabbit.

Influence of gender on control of arterial tone in experimental hypertension

Endothelial dysfunction has been found to be less severe in female than in male spontaneously hypertensive rats (SHR), which could contribute to the gender differences observed in the extent and rate of progression of hypertension in SHR. However, the influence of gender on the roles of different endothelium-derived mediators in the arterial responses in hypertension have not been evaluated in detail. Therefore, contractile and relaxation responses of mesenteric arterial rings in vitro were studied in female and male SHR, with normotensive female and male Wistar-Kyoto rats (WKY) serving as controls. In norepinephrine (NE)-precontracted arterial rings, endothelium-dependent relaxations to ACh as well as endothelium-independent dilations to sodium nitroprusside were more pronounced in female than in male SHR, whereas relaxations to the β-adrenoceptor agonist isoproterenol remained equally impaired in female and male SHR. The cyclooxygenase inhibitor diclofenac, which reduces the synthesis of dilating and constricting prostanoids, markedly enhanced the relaxations to ACh in male SHR but not in the other groups. The nitric oxide (NO) synthase inhibitor N G-nitro-l-arginine methyl ester attenuated the relaxations to ACh more effectively in female SHR and WKY than in the male groups. However, when endothelium-dependent hyperpolarization was prevented by precontracting the preparations with KCl, no significant differences were found in relaxations to ACh among the study groups. In conclusion, release of cyclooxygenase-derived constricting factors appeared to be more pronounced in male than in female SHR. In addition, the relative role of NO in endothelium-dependent arterial relaxation seemed to be higher in female than in male SHR, and relaxation induced by an NO donor also was more pronounced in female than in male SHR.Endothelial dysfunction has been found to be less severe in female than in male spontaneously hypertensive rats (SHR), which could contribute to the gender differences observed in the extent and rate of progression of hypertension in SHR. However, the influence of gender on the roles of different endothelium-derived mediators in the arterial responses in hypertension have not been evaluated in detail. Therefore, contractile and relaxation responses of mesenteric arterial rings in vitro were studied in female and male SHR, with normotensive female and male Wistar-Kyoto rats (WKY) serving as controls. In norepinephrine (NE)-precontracted arterial rings, endothelium-dependent relaxations to ACh as well as endothelium-independent dilations to sodium nitroprusside were more pronounced in female than in male SHR, whereas relaxations to the beta-adrenoceptor agonist isoproterenol remained equally impaired in female and male SHR. The cyclooxygenase inhibitor diclofenac, which reduces the synthesis of dilating and constricting prostanoids, markedly enhanced the relaxations to ACh in male SHR but not in the other groups. The nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester attenuated the relaxations to ACh more effectively in female SHR and WKY than in the male groups. However, when endothelium-dependent hyperpolarization was prevented by precontracting the preparations with KCl, no significant differences were found in relaxations to ACh among the study groups. In conclusion, release of cyclooxygenase-derived constricting factors appeared to be more pronounced in male than in female SHR. In addition, the relative role of NO in endothelium-dependent arterial relaxation seemed to be higher in female than in male SHR, and relaxation induced by an NO donor also was more pronounced in female than in male SHR.

Exercise enhances vasorelaxation in experimental obesity associated hypertension

OBJECTIVE Regular exercise is recommended for the non-pharmacological treatment of hypertension, but the mechanisms underlying the lowering of blood pressure remain controversial. Therefore, we studied the effects of 22-week-long training on blood pressure, arterial reactivity, and metabolic abnormalities in a model of genetic obesity and moderate hypertension. METHODS Obese and lean Zucker rats were subjected to treadmill exercise from 8 to 30 weeks of age. Blood pressures were measured by the tail-cuff method, and urine was collected in metabolic cages. At the end of the study, the samples for biochemical determinations were taken, and reactivity of isolated mesenteric and carotid arterial rings was examined in standard organ chambers. RESULTS The exercise prevented the elevation of blood pressure which was observed in non-exercised obese Zucker rats, and also reduced blood pressure in the lean rats. The relaxations of norepinephrine-preconstricted mesenteric and carotid arterial rings to acetylcholine and nitroprusside were clearly improved by exercise in the obese rats. In the lean rats exercise enhanced vasorelaxation to nitroprusside in the mesenteric and carotid rings, and to acetylcholine in the carotid preparations. The exercise-induced improvement of endothelium-mediated dilatation to acetylcholine was abolished by nitric oxide synthesis inhibition with NG nitro-L-arginine methyl ester, but not by cyclooxygenase inhibition with diclofenac or functional inhibition of endothelium-dependent hyperpolarization by precontractions with KCl. The urinary excretion of the systemic prostacyclin metabolite (2,3-dinor-6-ketoprostaglandin F1 alpha) was increased two-fold by exercise in the obese and lean rats, whereas that of the thromboxane A2 metabolite (11-dehydrothromboxane B2) remained unaffected. Treadmill training reduced blood glucose, cholesterol, and triglycerides, but did not affect the high levels of insulin in obese Zucker rats. CONCLUSIONS These results suggest that the antihypertensive effect of long-term exercise in experimental obesity related hypertension is associated with improved vasodilatation. This is expressed as enhanced relaxation via endogenous and exogenous nitric oxide, and increased endothelial prostacyclin production. The improved control of arterial tone after training could be attributed to the alleviation of hyperlipidemia and insulin resistance, whereas hyperinsulinaemia per se remained unaffected.

The severity of Puumala hantavirus induced nephropathia epidemica can be better evaluated using plasma interleukin-6 than C-reactive protein determinations

BackgroundNephropathia epidemica (NE) is a Scandinavian type of hemorrhagic fever with renal syndrome caused by Puumala hantavirus. The clinical course of the disease varies greatly in severity. The aim of the present study was to evaluate whether plasma C-reactive protein (CRP) and interleukin (IL)-6 levels associate with the severity of NE.MethodsA prospectively collected cohort of 118 consecutive hospital-treated patients with acute serologically confirmed NE was examined. Plasma IL-6, CRP, and creatinine, as well as blood cell count and daily urinary protein excretion were measured on three consecutive days after admission. Plasma IL-6 and CRP levels higher than the median were considered high.ResultsWe found that high IL-6 associated with most variables reflecting the severity of the disease. When compared to patients with low IL-6, patients with high IL-6 had higher maximum blood leukocyte count (11.9 vs 9.0 × 109/l, P = 0.001) and urinary protein excretion (2.51 vs 1.68 g/day, P = 0.017), as well as a lower minimum blood platelet count (55 vs 80 × 109/l, P < 0.001), hematocrit (0.34 vs 0.38, P = 0.001), and urinary output (1040 vs 2180 ml/day, P < 0.001). They also stayed longer in hospital than patients with low IL-6 (8 vs 6 days, P < 0.001). In contrast, high CRP did not associate with severe disease.ConclusionsHigh plasma IL-6 concentrations associate with a clinically severe acute Puumala hantavirus infection, whereas high plasma CRP as such does not reflect the severity of the disease.

Endothelial function in spontaneously hypertensive rats: influence of quinapril treatment

1 Angiotensin converting enzyme (ACE) inhibition has been shown to restore the impaired endothelial function in hypertension, but the mediators underlying the promoted endothelium‐dependent dilatation have not been fully characterized. Therefore, we investigated the effects of 10‐week‐long quinapril therapy (10 mg kg−1 day−1) on responses of mesenteric arterial rings in vitro from spontaneously hypertensive rats (SHR) and normotensive Wistar‐Kyoto (WKY) rats. 2 Endothelium‐dependent relaxations of noradrenaline (NA)‐precontracted rings to acetylcholine (ACh) and adenosine 5′‐diphosphate (ADP) were similar in WKY rats and quinapril‐treated SHR and more pronounced than in untreated SHR. The nitric oxide (NO) synthase inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME) attenuated the relaxations in both WKY groups and quinapril‐treated SHR, and completely inhibited them in untreated SHR. When endothelium‐dependent hyperpolarization was prevented by precontraction of the preparations with potassium chloride (KC1), no differences were found in relaxations to ACh and ADP between the study groups. In addition, in NA‐precontracted rings the L‐NAME‐ and indomethacin‐resistant relaxations to ACh were partially prevented by apamin, an inhibitor of calcium‐activated potassium channels. 3 Interestingly, in quinapril‐treated SHR but not in the other groups, exogenous bradykinin potentiated the relaxations to ACh in both NA‐ and KCl‐precontracted arterial rings. 4 Contractile sensitivity of endothelium‐intact rings to NA was reduced in SHR by quinapril, and was more effectively increased by L‐NAME in quinapril‐treated than untreated SHR. 5 In conclusion, since the relaxations to ACh and ADP in quinapril‐treated SHR were augmented in the absence and presence of NO synthesis inhibition but not under conditions which prevented hyperpolarization, enhanced endothelium‐dependent relaxation after long‐term ACE inhibition can be attributed to increased endothelium‐dependent hyperpolarization. However, the potentiation of the response to ACh by exogenous bradykinin in quinapril‐treated SHR, as well as the increased attenuating effect of the endothelium on NA‐induced contractions in these animals appear to result from enhanced endothelium‐derived NO release.

Analysis of cardiovascular responses to passive head‐up tilt using continuous pulse wave analysis and impedance cardiography

Objective. To non‐invasively measure central haemodynamics, arterial stiffness, cardiac function and vascular resistance, with the subject in the supine position and during head‐up tilt, in order to examine the haemodynamic changes associated with alterations in the augmentation index, and to investigate repeatability and reproducibility of the measurement protocol. Material and methods. Thirty‐three healthy volunteers (21–51 years) were investigated using continuous pulse wave analysis from the radial artery with a tonometric sensor, whole‐body impedance cardiography and plethysmographic blood pressure (BP) recordings from the fingers. The measurements were performed with the subject supine and during passive head‐up tilt, and repeated during the same session and on four separate days. Results. During the head‐up tilt, diastolic BP (5.2±0.6 %), heart rate (27.6±1.9 %) and vascular resistance (12.5±1.7 %) increased (all p<0.05), while systolic BP (−3.2±0.6 %), aortic pulse pressure (−23.3±1.4 %), augmentation index (−11.6±0.7 %), aortic reflection time (−7.0±1.0 %), ejection duration (−21.4±0.7 %), stroke volume (−26.1±1.2 %) and cardiac output (−5.0±1.5 %) decreased (all p<0.05). Augmentation index at rest correlated with aortic systolic BP (r = 0.423), aortic reflection time (r = −0.647), pulse wave velocity (r = 0.287) and age (r = 0.480). The change in augmentation index during head‐up tilt correlated with the change in aortic systolic BP (r = 0.469), aortic pulse pressure (r = 0.606), ejection duration (r = 0.374) and heart rate (r = −0.445). According to Bland‐Altman and repeatability index analyses, repeatability and reproducibility of the measurements were good during the same session and on separate days. Conclusions. Combined pulse wave analysis and impedance cardiography with the subject in the supine position and during head‐up tilt is a repeatable and reproducible method for comprehensive investigation of the cardiovascular function.

Endothelial Function in Deoxycorticosterone-NaCl Hypertension Effect of Calcium Supplementation

BACKGROUND Dietary calcium intake has been suggested to correlate inversely with blood pressure in humans and experimental animals. However, the effects of calcium supplementation on hypertensive disturbances of the endothelium have not been well characterized. METHODS AND RESULTS Wistar-Kyoto rats made hypertensive by deoxycorticosterone (DOC)-NaCl treatment, but a concurrent increase in chow calcium content from 1.1% to 2.5% markedly attenuated the rise in blood pressure. The function of isolated mesenteric arterial rings in vitro was investigated at the close of the 10-week study. In norepinephrine-precontracted rings, the relaxations to acetylcholine (ACh) and ADP, as well as to nitroprusside, 3-morpholinosydnonimine, and isoproterenol were attenuated in hypertensive rats on 1.1% calcium supplementation. In the presence of NG-nitro-L-arginine methyl ester (L-NAME), the relaxations to ACh in hypertensive animals on normal calcium were practically absent, whereas in normotensive rats and calcium-supplemented hypertensive rats, distinct relaxations to higher concentrations of ACh were still present. These responses were reduced by 30% to 50% with apamin, a blocker of Ca2+-activated K+ channels, and were further inhibited by blockade of ATP-dependent K+ channels with glyburide. Interestingly, relaxations elicited by ACh and ADP during precontraction with 60 mmol/L KCl (preventing endothelium-dependent hyperpolarization) were not impaired in hypertensive animals. The contractile sensitivity of endothelium-intact arterial rings to 5-hydroxytryptamine and norepinephrine was higher in hypertensive rats on either normal or high-calcium diet, whereas the increase in contractile sensitivity caused by L-NAME corresponded in all groups. CONCLUSION High-calcium diet markedly opposed experimental DOC-NaCl hypertension, an effect associated with improved arterial relaxation, while abnormalities of vascular contractile properties remained unaffected. In particular, the hyperpolarization-related component of endothelium-dependent arterial relaxation, mediated via opening of arterial K+ channels, could be augmented by calcium supplementation in DOC-NaCl hypertension.

Effects of botulinum toxin A on the sphincter of Oddi: an in vivo and in vitro study

Background—Botulinum toxin A is a potent inhibitor of the release of acetylcholine from nerve endings. Local injection of botulinum toxin has recently been suggested to be helpful in sphincter of Oddi dyskinesia by decreasing sphincter of Oddi pressure. Aims—To explore the mechanism of action of botulinum toxin A on sphincter of Oddi (SO) muscle. Methods—Four piglets underwent duodenoscopy and SO manometry was performed. After obtaining a baseline pressure, the SO was injected with normal saline and the experiment repeated after one week. The SO was then injected endoscopically with botulinum toxin (40 U) with follow up manometry one week later. The sphincter of Oddi was removed from 10 pigs, cut into three rings, and placed in an organ bath. The force of contraction was measured and registered on a polygraph. Rings were stimulated by 70 V (10 Hz, 0.5 ms) electrical field stimulation for 20 seconds, exogenous acetylcholine (100 μM), and KCl (125 mM). Botulinum toxin (0.1 U/ml) or atropine (1 μM) was added to the incubation medium and the stimulation was repeated. Results—Mean basal SO pressure in the pigs remained unchanged after saline injection but decreased to about 50% of baseline value following botulinum toxin injection (p=0.04). The contractions induced by direct stimulation of SO smooth muscle with KCl were not significantly affected by either atropine or botulinum toxin. In all rings exogenous acetylcholine induced contractions, which were totally blocked by atropine, but not by botulinum toxin. Electrical field stimulation induced contractions that were inhibited by both atropine and botulinum toxin. Conclusion—Botulinum toxin inhibits pig sphincter of Oddi smooth muscle contractions by a presynaptic cholinergic mechanism, similar to that described in skeletal muscle.