Biomedical subjects

Ingrid M Garrelds

Publications and source records attributed to Ingrid M Garrelds.

17 recordsLinked to original sources

PubMed2006

Effects of current and prospective antimigraine drugs on the porcine isolated meningeal artery.

Vasoconstriction to agonists at serotonin (5-hydroxytryptamine; 5-HT) receptors and alpha-adrenoceptors, as well as vasodilatation induced by alpha-CGRP, have been well described in the porcine carotid circulation in vivo. The present study sets out to investigate the effects of current and prospective antimigraine drugs on porcine meningeal artery segments in vitro. Sumatriptan, ergotamine, dihydroergotamine, isometheptene and clonidine failed to contract the meningeal artery, but 5-HT, noradrenaline and phenylephrine induced concentration-dependent contractions. The contractions to 5-HT were competitively antagonized by the 5-HT(2A) receptor antagonist ketanserin, whilst those to noradrenaline were antagonized by alpha(1)-(prazosin), alpha(2)-(rauwolscine and yohimbine) and alpha(2C/2B)-(OPC-28326) adrenoceptor antagonists. Whilst dobutamine and salbutamol were ineffective, alpha-CGRP produced concentration-dependent relaxations that were antagonized by the CGRP(1) receptor antagonist olcegepant. In agreement with their lack of contractile effect, sumatriptan and ergotamine failed to influence forskolin-stimulated cyclic AMP accumulation in the porcine meningeal artery; in contrast, both compounds decreased forskolin-stimulated cyclic AMP accumulation in the human isolated saphenous vein, where they induced contractions. Finally, using RT-PCR, we could demonstrate the presence of mRNAs encoding for several 5-HT receptors (5-HT(1B), 5-HT(1D), 5-HT(1F), 5-HT(2A) and 5-HT(7)) and adrenoceptors (alpha(1A), alpha(1B), alpha(1D), alpha(2A), alpha(2B), alpha(2C), beta(1) and beta(2)), as well as that for the calcitonin receptor like receptor, a component of the CGRP(1) receptor. These results suggest that: (i) the porcine meningeal artery may not be involved in the vasoconstriction of the carotid vascular bed elicited by antimigraine drugs in anaesthetized pigs, and (ii) the mismatch between the presence of receptor mRNA and the lack of response to sumatriptan, dobutamine and salbutamol implies that mRNAs for the 5-HT(1B) receptor and beta(1)- and beta(2)-adrenoceptors are probably unstable, or that their density is too low for being translated as receptor protein in sufficient quantities.

Adrenergic alpha-Agonists↗

PubMed2006

Prorenin induces intracellular signaling in cardiomyocytes independently of angiotensin II.

Tissue accumulation of circulating prorenin results in angiotensin generation, but could also, through binding to the recently cloned (pro)renin receptor, lead to angiotensin-independent effects, like p42/p44 mitogen-activated protein kinase (MAPK) activation and plasminogen-activator inhibitor (PAI)-1 release. Here we investigated whether prorenin exerts angiotensin-independent effects in neonatal rat cardiomyocytes. Polyclonal antibodies detected the (pro)renin receptor in these cells. Prorenin affected neither p42/p44 MAPK nor PAI-1. PAI-1 release did occur during coincubation with angiotensinogen, suggesting that this effect is angiotensin mediated. Prorenin concentration-dependently activated p38 MAPK and simultaneously phosphorylated HSP27. The latter phosphorylation was blocked by the p38 MAPK inhibitor SB203580. Rat microarray gene (n=4800) transcription profiling of myocytes stimulated with prorenin detected 260 regulated genes (P<0.001 versus control), among which genes downstream of p38 MAPK and HSP27 involved in actin filament dynamics and (cis-)regulated genes confined in blood pressure and diabetes QTL regions, like Syntaxin-7, were overrepresented. Quantitative real-time RT-PCR of 7 selected genes (Opg, Timp1, Best5, Hsp27, pro-Anp, Col3a1, and Hk2) revealed temporal regulation, with peak levels occurring after 4 hours of prorenin exposure. This regulation was not altered in the presence of the renin inhibitor aliskiren or the angiotensin II type 1 receptor antagonist eprosartan. Finally, pilot 2D proteomic differential display experiments revealed actin cytoskeleton changes in cardiomyocytes after 48 hours of prorenin stimulation. In conclusion, prorenin exerts angiotensin-independent effects in cardiomyocytes. Prorenin-induced stimulation of the p38 MAPK/HSP27 pathway, resulting in alterations in actin filament dynamics, may underlie the severe cardiac hypertrophy that has been described previously in rats with hepatic prorenin overexpression.

Actin Cytoskeleton↗

PubMed2006

Cardioprotective effects of eplerenone in the rat heart: interaction with locally synthesized or blood-derived aldosterone?

Mineralocorticoid receptor antagonism with eplerenone reduces mortality in heart failure, possibly because of blockade of the deleterious effects of aldosterone. To investigate these effects, rat Langendorff hearts were exposed to aldosterone and/or eplerenone. Under normal conditions, aldosterone increased left ventricular pressure and decreased coronary flow. Eplerenone did not block these effects. Eplerenone reduced infarct size (from 68+/-2% to 53+/-4%; P<0.05) and increased left ventricular pressure recovery (from 44+/-2% to 60+/-5%; P<0.05) after 45 minutes of coronary artery occlusion and 3 hours of reperfusion, whereas aldosterone did not affect these parameters. To verify the origin of cardiac aldosterone, hearts were perfused with 3 to 30 nmol/L aldosterone and either frozen immediately or exposed to washout. Without washout, cardiac aldosterone was 1.5 times aldosterone in coronary effluent (CE), that is, too high to be explained on the basis of its presence in extracellular fluid. The cardiac levels of aldosterone correlated with its CE levels (r=0.81; P<0.01), and both were unaffected by eplerenone. During washout, tissue aldosterone disappeared monophasically (half life, 9+/-1 minutes), and CE aldosterone disappeared biphasically (half life 1+/-0 and 8+/-1 minutes, respectively). During buffer perfusion, cardiac aldosterone was at or below the detection limit. In conclusion, eplerenone improves the condition of the heart after ischemia and reperfusion. This does not relate to interference with the inotropic and vasoconstrictor effects of aldosterone. The majority of cardiac aldosterone, if not all, is derived from the circulation. The rapid, mineralocorticoid receptor-independent kinetics of aldosterone suggest that its accumulation in the heart involves cell surface binding rather than internalization.

Aldosterone↗

PubMed2006

Elevated blood pressure and heart rate in human renin receptor transgenic rats.

Recently, a receptor for renin was described that may be important for vascular uptake and activation of (pro)renin, thus leading to local generation of angiotensin II. To assess the in vivo relevance of this protein, we generated transgenic rats overexpressing the human renin receptor gene in smooth muscle tissue, under the control of a 16-kb fragment of the mouse smooth muscle myosin heavy chain gene [TGR(SMMHC-HRR)]. Four lines of transgenic animals were obtained. The correct pattern of expression of the transgene was confirmed by RNase protection assay and in situ hybridization. TGR(SMMHC-HRR) rats are fertile and develop normally. After 6 months of age, transgenic rats develop a cardiovascular phenotype with an elevated systolic blood pressure (137.8+/-5 versus 118.9+/-3.7 mm Hg; P=0.008), and an augmentation in heart rate (349.1+/-7.7 versus 303.1+/-16.16 bpm; P=0.023) in TGR(SMMHC-HRR) and controls, respectively. These alterations are progressively increasing with aging. Although kidney function and plasma renin were normal in TGR(SMMHC-HRR), an increase in plasma aldosterone [TGR(SMMHC-HRR) 428+/-64.9 versus 207.3+/-73.24 pg/mL in control; P=0.02] and in aldosterone/renin ratio [TGR(SMMHC-HRR) 8.04+/-2.2 versus 2.8+/-0.55 in control; P=0.03] was observed. This suggests that renin receptor overexpression has resulted in increased intraadrenal angiotensin II, thereby provoking enhanced aldosterone generation in the absence of changes in plasma renin. The rise in aldosterone may underlie, at least in part, the observed cardiovascular phenotype of TGR(SMMHC-HRR).

Aldosterone↗

PubMed2006

Carvedilol-induced antagonism of angiotensin II: a matter of alpha1-adrenoceptor blockade.

OBJECTIVE: To investigate whether renin-angiotensin system blockade might underlie the favorable metabolic effects of the nonselective beta + alpha1-adrenoceptor blocker carvedilol as compared with the selective beta1-adrenoceptor blocker metoprolol. METHODS: Human coronary microarteries (HCMAs), obtained from 32 heart valve donors, were mounted in myographs. RESULTS: Angiotensin II and the alpha1-adrenoceptor agonist phenylephrine constricted HCMAs to maximally 63 +/- 10 and 46 +/- 15% of the contraction to 100 mmol/l K. Neither carvedilol, metoprolol, the nonselective beta-adrenoceptor antagonist propranolol, nor the alpha1-adrenoceptor antagonist prazosin affected the constrictor response to angiotensin II. alpha1-adrenoreceptors and beta-adrenoceptors are thus not involved in the direct constrictor effects of angiotensin II. When added to the organ bath at a subthreshold concentration, angiotensin II greatly amplified the response to phenylephrine. Both carvedilol and the angiotensin II type 1 (AT1) receptor antagonist irbesartan inhibited this angiotensin II-induced potentiation. Furthermore, carvedilol blocked the angiotensin II-induced amplification of phenylephrine-induced inositol phosphate accumulation in cardiomyocytes. CONCLUSIONS: AT1-alpha1-receptor crosstalk, involving inositol phosphates, sensitizes HCMAs to alpha1-adrenoceptor agonists. Our results suggest that, in the presence of an increased sympathetic tone, carvedilol provides AT1 receptor blockade via its alpha1-adrenoceptor blocking effects. This could explain the favorable effects of carvedilol versus metoprolol.

Adolescent↗

PubMed2005

Characterisation of CGRP receptors in human and porcine isolated coronary arteries: evidence for CGRP receptor heterogeneity.

This study sets out to characterise calcitonin gene-related peptide (CGRP) receptors in human and porcine isolated proximal and distal coronary arteries using BIBN4096BS. Human (h)-alphaCGRP induced relaxations that were blocked by BIBN4096BS in all arteries studied. In contrast to the other vessels, the Schild plot slope in the human distal coronary artery segments (0.68 +/- 0.07) was significantly less than unity and BIBN4096BS potently blocked these responses (pK(b) (10 nM): 9.29 +/- 0.34, n = 5). In the same preparation, h-alphaCGRP(8-37) behaved as a weak antagonist of h-alphaCGRP-induced relaxations (pK(b) (3 microM): 6.28 +/- 0.17, n = 4), with also a Schild plot slope smaller than unity. The linear agonists, [ethylamide-Cys(2,7)]-h-alphaCGRP ([Cys(Et)(2,7)]-h-alphaCGRP) and [acetimidomethyl-Cys(2,7)]-h-alphaCGRP ([Cys(Acm)(2,7)]-h-alphaCGRP), had a high potency (pEC(50): 8.21 +/- 0.25 and 7.25 +/- 0.14, respectively), suggesting the presence of CGRP(2) receptors, while the potent blockade by BIBN4096BS (pK(b) (10 nM): 10.13 +/- 0.29 and 9.95 +/- 0.11, respectively) points to the presence of CGRP(1) receptors. Using RT-PCR, mRNAs encoding for the essential components for functional CGRP(1) receptors were demonstrated in both human proximal and distal coronary artery. Further, h-alphaCGRP (100 nM) increased cAMP levels, and this was attenuated by BIBN4096BS (1 microM). The above results demonstrate the presence of CGRP(1) receptors in all coronary artery segments investigated, but the human distal coronary artery segments seem to have an additional population of CGRP receptors not complying with the currently classified CGRP(1) or CGRP(2) receptors.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed2005

Nongenomic effects of aldosterone in the human heart: interaction with angiotensin II.

Aldosterone exerts rapid "nongenomic" effects in various nonrenal tissues. Here, we investigated whether such effects occur in the human heart. Trabeculae and coronary arteries obtained from 57 heart valve donors (25 males; 32 females; 17 to 66 years of age) were mounted in organ baths. Aldosterone decreased contractility in atrial and ventricular trabeculae by maximally 34+/-3% and 15+/-4%, respectively, within 5 to 15 minutes after its application. The protein kinase C (PKC) inhibitor chelerythrine chloride, but not the mineralocorticoid receptor antagonists spironolactone and eplerenone, blocked this effect. Aldosterone also relaxed trabeculae that were prestimulated with angiotensin II (Ang II), and its negative inotropic effects were mimicked by hydrocortisone (at 10-fold lower potency) but not 17beta-estradiol. Aldosterone concentrations required to reduce inotropy were present in failing but not in normal human hearts. Previous exposure of coronary arteries to 1 micromol/L aldosterone or 17beta-estradiol (but not hydrocortisone) doubled the maximum contractile response (Emax) to Ang II. DeltaEmax correlated with extracellular signal-regulated kinase (ERK) 1/2 phosphorylation (P<0.01). Spironolactone and eplerenone did not block the potentiating effect of aldosterone. Studies in porcine renal arteries showed that potentiation also occurred at pmol/L aldosterone levels but not at 17beta-estradiol levels <1 micromol/L. Aldosterone did not potentiate the alpha1-adrenoceptor agonist phenylephrine. In conclusion, aldosterone induces a negative inotropic response in human trabeculae (thereby antagonizing the positive inotropic actions of Ang II) and potentiates the vasoconstrictor effect of Ang II in coronary arteries. These effects are specific and involve PKC and ERK 1/2, respectively. Furthermore, they occur in a nongenomic manner, and require pathological aldosterone concentrations.

Adolescent↗

PubMed2005

Aliskiren, a human renin inhibitor, ameliorates cardiac and renal damage in double-transgenic rats.

We tested the hypothesis that the renin inhibitor aliskiren ameliorates organ damage in rats transgenic for human renin and angiotensinogen genes (double transgenic rat [dTGR]). Six-week-old dTGR were matched by albuminuria (2 mg per day) and divided into 5 groups. Untreated dTGR were compared with aliskiren (3 and 0.3 mg/kg per day)-treated and valsartan (Val; 10 and 1 mg/kg per day)-treated rats. Treatment was from week 6 through week 9. At week 6, all groups had elevated systolic blood pressure (BP). Untreated dTGR showed increased BP (202+/-4 mm Hg), serum creatinine, and albuminuria (34+/-5.7 mg per day) at week 7. At week 9, both doses of aliskiren lowered BP (115+/-6 and 139+/-5 mm Hg) and albuminuria (0.4+/-0.1 and 1.6+/-0.6 mg per day) and normalized serum creatinine. Although high-dose Val lowered BP (148+/-4 mm Hg) and albuminuria (2.1+/-0.7 mg per day), low-dose Val reduced BP (182+/-3 mm Hg) and albuminuria (24+/-3.8 mg per day) to a lesser extent. Mortality was 100% in untreated dTGR and 26% in Val (1 mg/kg per day) treated rats, whereas in all other groups, survival was 100%. dTGR treated with low-dose Val had cardiac hypertrophy (4.4+/-0.1 mg/g), increased left ventricular (LV) wall thickness, and diastolic dysfunction. LV atrial natriuretic peptide and beta-myosin heavy chain mRNA, albuminuria, fibrosis, and cell infiltration were also increased. In contrast, both aliskiren doses and the high-dose Val lowered BP to a similar extent and more effectively than low-dose Val. We conclude that in dTGR, equieffective antihypertensive doses of Val or aliskiren attenuated end-organ damage. Thus, renin inhibition compares favorably to angiotensin receptor blockade in reversing organ damage in dTGR.

Albuminuria↗

PubMed2005

Mechanical unloading during left ventricular assist device support increases left ventricular collagen cross-linking and myocardial stiffness.

BACKGROUND: Left ventricular assist devices (LVADs) induce reverse remodeling of the failing heart except for the extracellular matrix, which exhibits additional pathophysiological changes, although their mechanisms and functional consequences are unknown. METHODS AND RESULTS: Hearts were obtained at transplant from patients with idiopathic dilated cardiomyopathy (DCM) not requiring LVAD support (n=30), patients requiring LVAD support (n=16; LVAD duration, 145+/-33 days), and 5 nonfailing hearts. Left (LV) and right ventricular (RV) ex vivo pressure-volume relationships were measured, and chamber and myocardial stiffness constants were determined. Myocardial tissue content of total and cross-linked collagen, collagen types I and III, MMP-1, MMP-9, TIMP-1, and angiotensin (Ang) I and II were measured. LV size, mass, and myocyte diameter decreased after LVAD compared with DCM without LVAD (P<0.05). Total and cross-linked collagen and ratio of type I to III collagen increased in DCM compared with nonfailing hearts and increased further after LVAD (P<0.05 versus DCM and nonfailing). Concomitantly, chamber and myocardial stiffness increased with LVAD. The ratio of MMP-1 to TIMP-1 increased in DCM and almost normalized after LVAD, favoring decreased collagen degradation. Tissue Ang I and II also increased during LVAD. There was no significant change in the RV of LVAD-supported heart compared with DCM. CONCLUSIONS: LVAD support increases LV collagen cross-linking and the ratio of collagen type I to III, which is associated with increased myocardial stiffness. Decreased tissue MMP-1-to-TIMP-1 ratio (decreased degradation) and increased Ang levels (stimulants of synthesis) are likely mechanisms for these changes. Lack of significant effects on the RV suggest that hemodynamic unloading of the LV (not provided to the RV) might be the primary factor that regulates these extracellular matrix changes.

Adult↗

PubMed2005

Genomic and nongenomic effects of aldosterone in the rat heart: why is spironolactone cardioprotective?

1. Mineralocorticoid receptor (MR) antagonism with spironolactone reduces mortality in heart failure on top of ACE inhibition. To investigate the underlying mechanism, we compared the actions of both aldosterone and spironolactone to those of angiotensin (Ang) II in the rat heart. 2. Hearts of male Wistar rats were perfused according to Langendorff. Ang II and aldosterone increased left ventricular pressure (LVP) by maximally 11+/-4 and 9+/-2%, and decreased coronary flow (CF) by maximally 36+/-7 and 20+/-4%, respectively. Spironolactone did not significantly affect LVP or CF. 3. In hearts that were exposed to a 45-min coronary artery occlusion and 3 h of reperfusion, a 15-min exposure to spironolactone prior to occlusion reduced infarct size (% of risk area) from 68+/-2 to 45+/-3%, similar to the reduction (34+/-2%) observed following 'preconditioning' (15 min occlusion followed by 10 min reperfusion) prior to the 45-min occlusion. Aldosterone exposure did not affect infarct size (71+/-5%). 4. In cardiomyocytes, aldosterone decreased [(3)H]thymidine incorporation maximally by 73+/-3%, whereas in cardiac fibroblasts it decreased [(3)H]proline incorporation by 33+/-7%. Spironolactone inhibited both effects. Ang II increased DNA and collagen synthesis, and these effects were reversed by aldosterone. 5. In conclusion, aldosterone induces positive inotropic and vasoconstrictor effects in a nongenomic manner, and these effects are comparable to those of Ang II. Aldosterone reduces DNA and collagen synthesis via MR activation, and counteracts the Ang II-induced increases in these parameters. MR blockade reduces infarct size and increases LVP recovery following coronary artery occlusion. The MR-related phenomena may underlie, at least in part, the beneficial actions of spironolactone in heart failure.

Aldosterone↗

PubMed2004

Angiotensin II type 2 receptor-mediated vasodilation in human coronary microarteries.

BACKGROUND: Angiotensin (Ang) II type 2 (AT2) receptor stimulation results in coronary vasodilation in the rat heart. In contrast, AT2 receptor-mediated vasodilation could not be observed in large human coronary arteries. We studied Ang II-induced vasodilation of human coronary microarteries (HCMAs). METHODS AND RESULTS: HCMAs (diameter, 160 to 500 microm) were obtained from 49 heart valve donors (age, 3 to 65 years). Ang II constricted HCMAs, mounted in Mulvany myographs, in a concentration-dependent manner (pEC50, 8.6+/-0.2; maximal effect [E(max)], 79+/-13% of the contraction to 100 mmol/L K+). The Ang II type 1 receptor antagonist irbesartan prevented this vasoconstriction, whereas the AT2 receptor antagonist PD123319 increased E(max) to 97+/-14% (P<0.05). The increase in E(max) was larger in older donors (correlation DeltaE(max) versus age, r=0.47, P<0.05). The PD123319-induced potentiation was not observed in the presence of the NO synthase inhibitor L-NAME, the bradykinin type 2 (B2) receptor antagonist Hoe140, or after removal of the endothelium. Ang II relaxed U46619-preconstricted HCMAs in the presence of irbesartan by maximally 49+/-16%, and PD123319 prevented this relaxation. Finally, radioligand binding studies and reverse transcription-polymerase chain reaction confirmed the expression of AT2 receptors in HCMAs. CONCLUSIONS: AT2 receptor-mediated vasodilation in the human heart appears to be limited to coronary microarteries and is mediated by B2 receptors and NO. Most likely, AT2 receptors are located on endothelial cells, and their contribution increases with age.

Adolescent↗

PubMed2004

Bradykinin-induced relaxation of coronary microarteries: S-nitrosothiols as EDHF?

1. To investigate whether S-nitrosothiols, in addition to NO, mediate bradykinin-induced vasorelaxation, porcine coronary microarteries (PCMAs) were mounted in myographs. 2. Following preconstriction, concentration-response curves (CRCs) were constructed to bradykinin, the NO donors S-nitroso-N-penicillamine (SNAP) and diethylamine NONOate (DEA-NONOate) and the S-nitrosothiols L-S-nitrosocysteine (L-SNC) and D-SNC. All agonists relaxed PCMAs. L-SNC was approximately 5-fold more potent than D-SNC. 3. The guanylyl cyclase inhibitor ODQ and the NO scavenger hydroxocobalamin induced a larger shift of the bradykinin CRC than the NO synthase inhibitor L-NAME, although all three inhibitors equally suppressed bradykinin-induced cGMP responses. 4. Complete blockade of bradykinin-induced relaxation was obtained with L-NAME in the presence of the large- and intermediate-conductance Ca(2+)-activated K(+)-channel (BK(Ca), IK(Ca)) blocker charybdotoxin and the small-conductance Ca(2+)-activated K(+)-channel (SK(Ca)) channel blocker apamin, but not in the presence of L-NAME, apamin and the BK(Ca) channel blocker iberiotoxin. 5. Inhibitors of cytochrome P450 epoxygenase, cyclooxygenase, voltage-dependent K(+) channels and ATP-sensitive K(+) channels did not affect bradykinin-induced relaxation. 6. SNAP-, DEA-NONOate- and D-SNC-induced relaxations were mediated entirely by the NO-guanylyl cyclase pathway. L-SNC-induced relaxations were partially blocked by charybdotoxin+apamin, but not by iberiotoxin+apamin, and this blockade was abolished following endothelium removal. ODQ, but not hydroxocobalamin, prevented L-SNC-induced increases in cGMP, and both drugs shifted the L-SNC CRC 5-10-fold to the right. 7. L-SNC hyperpolarized intact and endothelium-denuded coronary arteries. 8. Our results support the concept that bradykinin-induced relaxation is mediated via de novo synthesized NO and a non-NO, endothelium-derived hyperpolarizing factor (EDHF). S-nitrosothiols, via stereoselective activation of endothelial IK(Ca) and SK(Ca) channels, and through direct effects on smooth muscle cells, may function as an EDHF in porcine coronary microarteries.

Animals↗

PubMed2003

Mediators of bradykinin-induced vasorelaxation in human coronary microarteries.

To investigate the mediators of bradykinin-induced vasorelaxation in human coronary microarteries (HCMAs), HCMAs (diameter approximately 300 microm) obtained from 42 heart valve donors (20 men and 22 women; age range, 3 to 65 years; mean age, 46 years) were mounted in Mulvany myographs. In the presence of the cyclooxygenase inhibitor indomethacin, bradykinin relaxed preconstricted HCMAs in a concentration-dependent manner. N(G)-nitro-L-arginine methyl ester and ODQ (inhibitors of nitric oxide [NO] synthase and guanylyl cyclase, respectively) and the NO scavenger hydroxocobalamin, either alone or in combination, shifted the bradykinin concentration-response curve to the right. Removal of H2O2 (with catalase), inhibition of cytochrome P450 epoxygenase (with sulfaphenazole or clotrimazole) or gap junctions (with 18alpha-glycyrrhetinic acid or carbenoxolone), and blockade of large- (BK(Ca)) and small- (SK(Ca)) conductance Ca2+-dependent K+ channels (with iberiotoxin and apamin), either alone or in addition to hydroxocobalamin, did not affect bradykinin. In contrast, complete blockade of bradykinin-induced relaxation was obtained when we combined the nonselective BK(Ca) and intermediate-conductance (IK(Ca)) Ca2+-dependent K+ channel blocker charybdotoxin and apamin with hydroxocobalamin. Charybdotoxin plus apamin alone were without effect. Inhibition of inwardly rectifying K+ channels (K(IR)) and Na+/K+-ATPase (with BaCl2 and ouabain, respectively) shifted the bradykinin concentration-response curve 10-fold to the right but did not exert an additional effect in the presence of hydroxocobalamin. In conclusion, bradykinin-induced relaxation in HCMAs depends on (1) the activation of guanylyl cyclase, K(IR), and Na(+)/K(+)-ATPase by NO and (2) IK(Ca) and SK(Ca) channels. The latter are activated by a factor other than NO. This factor is not a cytochrome P450 epoxygenase product or H2O2, nor does it depend on gap junctions or BK(Ca) channels.

8,11,14-Eicosatrienoic Acid↗

PubMed2003

Effects of the CGRP receptor antagonist BIBN4096BS on capsaicin-induced carotid haemodynamic changes in anaesthetised pigs.

1. Calcitonin gene-related peptide (CGRP), a potent vasodilator released from capsaicin-sensitive trigeminal sensory nerves, seems to be involved in the pathogenesis of migraine. Hence, CGRP receptor antagonists may serve as a novel treatment for migraine. This study was therefore designed to investigate the effects of BIBN4096BS (100, 300 and 1000 microg kg-1, i.v.), a potent and selective CGRP receptor antagonist, on capsaicin-induced carotid haemodynamic changes in anaesthetised pigs. Both vagosympathetic trunks were cut and phenylephrine was infused into the carotid artery (i.c.) to support carotid vascular tone. 2. Infusions of capsaicin (0.3, 1, 3 and 10 microg kg-1 min-1, i.c.) did not alter the heart rate, but dose-dependently increased the mean arterial blood pressure. This moderate hypertensive effect was not modified by BIBN4096BS. 3. Capsaicin infusion (10 microg kg-1 min-1, i.c.) increased total carotid, arteriovenous anastomotic and tissue blood flows and conductances as well as carotid pulsations, but decreased the difference between arterial and jugular venous oxygen saturations. These responses to capsaicin were dose-dependently blocked by BIBN4096BS. 4. Capsaicin infusion (10 microg kg-1 min-1, i.c.) more than doubled the jugular venous plasma concentration of CGRP. This effect was not blocked, but rather increased, by BIBN4096BS. 5. The above results show that BIBN4096BS behaves as a potent antagonist of capsaicin-induced carotid haemodynamic changes that are mediated via the release of CGRP. Therefore, this compound may prove effective in the treatment of migraine.

Anesthesia↗

PubMed2003

ACE-versus chymase-dependent angiotensin II generation in human coronary arteries: a matter of efficiency?

OBJECTIVE: The objective of this study was to investigate ACE- and chymase-dependent angiotensin I-to-II conversion in human coronary arteries (HCAs). METHODS AND RESULTS: HCA rings were mounted in organ baths, and concentration-response curves to angiotensin II, angiotensin I, and the chymase-specific substrate Pro(11)-D-Ala(12)-angiotensin I (PA-angiotensin I) were constructed. All angiotensins displayed similar efficacy. For a given vasoconstriction, bath (but not interstitial) angiotensin II during angiotensin I and PA-angiotensin I was lower than during angiotensin II, indicating that interstitial (and not bath) angiotensin II determines vasoconstriction. PA-angiotensin I increased interstitial angiotensin II less efficiently than angiotensin I. Separate inhibition of ACE (with captopril) and chymase (with C41 or chymostatin) shifted the angiotensin I concentration-response curve approximately 5-fold to the right, whereas a 10-fold shift occurred during combined ACE and chymase inhibition. Chymostatin, but not captopril and/or C41, reduced bath angiotensin II and abolished PA-Ang I-induced vasoconstriction. Perfused HCA segments, exposed luminally or adventitially to angiotensin I, released angiotensin II into the luminal and adventitial fluid, respectively, and this release was blocked by chymostatin. CONCLUSIONS: Both ACE and chymase contribute to the generation of functionally active angiotensin II in HCAs. However, because angiotensin II loss in the organ bath is chymase-dependent, ACE-mediated conversion occurs more efficiently (ie, closer to AT(1) receptors) than chymase-mediated conversion.

Adolescent↗

PubMed2003

Effect of pharmacologically induced smooth muscle activation on permeability in murine colitis.

BACKGROUND: Both intestinal permeability and contractility are altered in inflammatory bowel disease. Little is known about their mutual relation. Therefore, an in vitro organ bath technique was developed to investigate the simultaneous effects of inflammation on permeability and smooth muscle contractility in different segments of the colon. METHODS AND MATERIALS: BALB/c mice were exposed to a 10% dextran sulphate sodium drinking water solution for 7 days to induce a mild colitis, while control mice received normal tap water. Intestinal segments were placed in an oxygenated organ bath containing Krebs buffer. Permeability was measured by the transport of the marker molecules 3H-mannitol and 14C-polyethyleneglycol 4000. Contractility was measured through a pressure sensor. Smooth muscle relaxation was obtained by salbutamol and l-phenylephrine, whereas contraction was achieved by carbachol and 1-(3-chlorophenyl)-biguanide. RESULTS: The intensity of mucosal inflammation increased throughout the colon. Also, regional differences were observed in intestinal permeability. In both normal and inflamed distal colon segments, permeability was diminished compared with proximal colon segments and the non-inflamed ileum. Permeability in inflamed distal colon segments was significantly decreased compared with normal distal segments. Pharmacologically induced relaxation of smooth muscles did not affect this diminished permeability, although an increased motility positively affected permeability in inflamed and non-inflamed distal colon. CONCLUSIONS: Inflammation and permeability is inversely related. The use of pro-kinetics could counteract this disturbed permeability and, in turn, could regulate the disturbed production of inflammatory mediators.

Albuterol↗

PubMed2002

Intestinal blood flow in murine colitis induced with dextran sulfate sodium.

The aim of this study was to assess whether colitis induced by dextran sulfate sodium (DSS; 10% in tap water for 7 days) in BALB/c mice is associated with changes in intestinal blood flow. After anaesthesia, systemic hemodynamic variable and regional blood flows and resistances in various organs were measured in both control and DSS-treated mice. Mean arterial blood pressure was significantly lower in DSS-treated mice than in controls (56 +/- 4 vs 66 +/- 3 mm Hg; P < 0.05), but no differences were found in regional blood flows to or vascular resistances in the lungs, liver, stomach, small intestine (upper, middle, and lower part), cecum, mesentery + pancreas, spleen, kidneys, brain, and skin. However, compared to the control mice, blood flows in the middle (0.88 +/- 0.13 vs 0.55 +/- 0.09 ml/min/g; P < 0.05) and distal (0.69 +/- 0.11 vs 0.29 +/- 0.05 ml/min/g; P < 0.05) colon were significantly higher, and vascular resistances in the proximal (0.87 +/- 0.21 vs 1.36 +/- 0.21 mm Hg min/ml/100 g; P < 0.05), middle (0.60 +/- 0.10 vs 1.46 +/- 0.35 mm Hg min/ml 100 g; P < 0.05) as well as distal (0.90 +/- 0.25 vs 2.67 +/- 0.49 mm Hg min/ml/100 g; P < 0.05) colon were significantly lower in mice with experimental colitis. Interestingly, there was a gradient in the intestinal blood flow in control mice from the upper small intestine (2.79 +/- 0.72 ml/min/g) down to the distal colon (0.29 +/- 0.05 ml/min/g); such a gradient was also present in the colitis mice. It is concluded that DSS-induced colitis in mice is associated with microcirculatory disturbances in the colon, mainly in its middle and distal parts.

Animals↗