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de Hemptinne A, Marrannes R, Vanheel B. Influence of organic acids on intracellular pH. THE AMERICAN JOURNAL OF PHYSIOLOGY 1983; 245:C178-83. [PMID: 6614155 DOI: 10.1152/ajpcell.1983.245.3.c178] [Citation(s) in RCA: 109] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
By use of double-barreled pH-sensitive microelectrodes, intracellular pH was measured in isolated sheep cardiac Purkinje strands. After equimolar substitution of 20 mmol/l Cl- by several organic anions at constant extracellular pH 6.8, the rate of induced intracellular acidification was measured. For many organic acids tested, a relation was found between the rate of intracellular acidification and the product of their dissociation constant (pK'a) and diisopropylether-to-water partition ratio (p'). L-Lactate and pyruvate, and also cyanoacetate and alpha-ketobutyrate, caused faster acidifications than anticipated from their pK'a and p'. The rate of intracellular acidification, induced by L-lactate and pyruvate, was markedly depressed in the presence of 4 mmol/l alpha-cyano-4-hydroxycinnamate, a known inhibitor of the carrier-mediated pyruvate transport. The drug also had an effect on the acidification produced by cyanoacetate, alpha-ketobutyrate, glycolate, alpha-hydroxybutyrate, and alpha-chloropropionate, but not on that produced by propionate and acetate. L-Lactate caused a faster acidification than D-lactate. Our results suggest the existence of a facilitated diffusion for L-lactate, pyruvate, and some other organic acids in sheep Purkinje cells.
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Van de Voorde J, Vanheel B, Leusen I. Endothelium-dependent relaxation and hyperpolarization in aorta from control and renal hypertensive rats. Circ Res 1992; 70:1-8. [PMID: 1727681 DOI: 10.1161/01.res.70.1.1] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Endothelium-dependent relaxations are depressed in hypertension. In this study we investigated the possible involvement of endothelium-dependent smooth muscle hyperpolarization in this phenomenon. In isolated aortic segments from control rats, acetylcholine (10(-8)-10(-5) M) elicits relaxations after precontraction with norepinephrine (10(-7) M), and acetylcholine or carbachol (10(-5) M) induce smooth muscle hyperpolarization (10.6 +/- 0.9 mV). Both effects disappear after removal of the endothelium and are depressed by tetraethylammonium (3 x 10(-3) M), a rather nonspecific blocker of K+ channels, but not by glibenclamide (10(-5) M), a potent blocker of the ATP-regulated K+ channels, which has a marked effect on the relaxation induced by BRL 38227. The relaxation effect of acetylcholine is impaired in norepinephrine-contracted preparations from hypertensive rats but is not further depressed by tetraethylammonium. In aorta from hypertensive rats, hyperpolarization induced by carbachol was significantly reduced to a mean of only 21.8% of the values obtained in preparations from normotensive rats. From the relaxation-hyperpolarization relation obtained with BRL 38227 (opening K+ channels), it is derived that the endothelium-dependent hyperpolarization (approximately 10 mV) contributes for at least 20-30% of the maximal relaxation effect of acetylcholine on rat aorta. It is concluded that the diminished endothelium-dependent hyperpolarization may contribute to the depression of the endothelium-dependent relaxation in hypertension.
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Comparative Study |
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Vanheel B, Van de Voorde J. Evidence against the involvement of cytochrome P450 metabolites in endothelium-dependent hyperpolarization of the rat main mesenteric artery. J Physiol 1997; 501 ( Pt 2):331-41. [PMID: 9192305 PMCID: PMC1159481 DOI: 10.1111/j.1469-7793.1997.331bn.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
1. The influence of different inhibitors of cytochrome P450 mono-oxygenase on the endothelium-dependent and -independent hyperpolarization in the isolated rat main mesenteric artery was investigated. 2. Application of acetylcholine (ACh; 1 microM) for 10 min evoked an endothelium-dependent peak hyperpolarization of about 18 mV followed by a partial recovery to a level 7 mV more negative than the resting value (-50.2 +/- 0.5 mV). 3. Proadifen (30 microM) completely and reversibly inhibited the ACh-induced hyperpolarization. Conversely, the imidazole antimycotics clotrimazole (30 microM) and miconazole (100 microM) had less effect on the peak endothelium-dependent hyperpolarization. The suicide substrate inhibitors 17-octadecynoic acid (17-ODYA; 5 microM) and 1-aminobenzotriazole (1-ABT; 2 mM) did not significantly influence endothelium-dependent hyperpolarization. 4. The endothelium-independent hyperpolarization (16 mV) evoked by leveromakalim (300 nM) was completely inhibited by proadifen as well as by clotrimazole and miconazole but was not affected by 17-ODYA or 1-ABT. 5. These results do not support the view that the ACh-induced endothelium-dependent hyperpolarization in the rat mesenteric artery is mediated by cytochrome P450 mono-oxygenase metabolites. Proadifen and imidazole antimycotics impair the activation of ATP-regulated K+ channels in mesenteric artery cells, rendering non-specific inhibition of smooth muscle K+ channel activation an alternative explanation for the inhibitory influence of some (but not all) P450 inhibitors on endothelium-dependent hyperpolarization in this preparation.
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Blancquaert L, Baba SP, Kwiatkowski S, Stautemas J, Stegen S, Barbaresi S, Chung W, Boakye AA, Hoetker JD, Bhatnagar A, Delanghe J, Vanheel B, Veiga‐da‐Cunha M, Derave W, Everaert I. Carnosine and anserine homeostasis in skeletal muscle and heart is controlled by β-alanine transamination. J Physiol 2016; 594:4849-63. [PMID: 27062388 PMCID: PMC5009790 DOI: 10.1113/jp272050] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 03/05/2016] [Indexed: 01/04/2023] Open
Abstract
KEY POINTS Using recombinant DNA technology, the present study provides the first strong and direct evidence indicating that β-alanine is an efficient substrate for the mammalian transaminating enzymes 4-aminobutyrate-2-oxoglutarate transaminase and alanine-glyoxylate transaminase. The concentration of carnosine and anserine in murine skeletal and heart muscle depends on circulating availability of β-alanine, which is in turn controlled by degradation of β-alanine in liver and kidney. Chronic oral β-alanine supplementation is a popular ergogenic strategy in sports because it can increase the intracellular carnosine concentration and subsequently improve the performance of high-intensity exercises. The present study can partly explain why the β-alanine supplementation protocol is so inefficient, by demonstrating that exogenous β-alanine can be effectively routed toward oxidation. ABSTRACT The metabolic fate of orally ingested β-alanine is largely unknown. Chronic β-alanine supplementation is becoming increasingly popular for improving high-intensity exercise performance because it is the rate-limiting precursor of the dipeptide carnosine (β-alanyl-l-histidine) in muscle. However, only a small fraction (3-6%) of the ingested β-alanine is used for carnosine synthesis. Thus, the present study aimed to investigate the putative contribution of two β-alanine transamination enzymes, namely 4-aminobutyrate-2-oxoglutarate transaminase (GABA-T) and alanine-glyoxylate transaminase (AGXT2), to the homeostasis of carnosine and its methylated analogue anserine. We found that, when transfected into HEK293T cells, recombinant mouse and human GABA-T and AGXT2 are able to transaminate β-alanine efficiently. The reaction catalysed by GABA-T is inhibited by vigabatrin, whereas both GABA-T and AGXT2 activity is inhibited by aminooxyacetic acid (AOA). Both GABA-T and AGXT2 are highly expressed in the mouse liver and kidney and the administration of the inhibitors effectively reduced their enzyme activity in liver (GABA-T for vigabatrin; GABA-T and AGXT2 for AOA). In vivo, injection of AOA in C57BL/6 mice placed on β-alanine (0.1% w/v in drinking water) for 2 weeks lead to a 3-fold increase in circulating β-alanine levels and to significantly higher levels of carnosine and anserine in skeletal muscle and heart. By contrast, specific inhibition of GABA-T by vigabatrin did not affect carnosine and anserine levels in either tissue. Collectively, these data demonstrate that homeostasis of carnosine and anserine in mammalian skeletal muscle and heart is controlled by circulating β-alanine levels, which are suppressed by hepatic and renal β-alanine transamination upon oral β-alanine intake.
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Research Support, N.I.H., Extramural |
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Vanlander AV, Okun JG, de Jaeger A, Smet J, De Latter E, De Paepe B, Dacremont G, Wuyts B, Vanheel B, De Paepe P, Jorens PG, Van Regenmortel N, Van Coster R. Possible pathogenic mechanism of propofol infusion syndrome involves coenzyme q. Anesthesiology 2015; 122:343-52. [PMID: 25296107 DOI: 10.1097/aln.0000000000000484] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Propofol is a short-acting intravenous anesthetic agent. In rare conditions, a life-threatening complication known as propofol infusion syndrome can occur. The pathophysiologic mechanism is still unknown. Some studies suggested that propofol acts as uncoupling agent, others suggested that it inhibits complex I or complex IV, or causes increased oxidation of cytochrome c and cytochrome aa3, or inhibits mitochondrial fatty acid metabolism. Although the exact site of interaction is not known, most hypotheses point to the direction of the mitochondria. METHODS Eight rats were ventilated and sedated with propofol up to 20 h. Sequential biopsy specimens were taken from liver and skeletal muscle and used for determination of respiratory chain activities and propofol concentration. Activities were also measured in skeletal muscle from a patient who died of propofol infusion syndrome. RESULTS In rats, authors detected a decrease in complex II+III activity starting at low tissue concentration of propofol (20 to 25 µM), further declining at higher concentrations. Before starting anesthesia, the complex II+III/citrate synthase activity ratio in liver was 0.46 (0.25) and in skeletal muscle 0.23 (0.05) (mean [SD]). After 20 h of anesthesia, the ratios declined to 0.17 (0.03) and 0.12 (0.02), respectively. When measured individually, the activities of complexes II and III remained normal. Skeletal muscle from one patient taken in the acute phase of propofol infusion syndrome also shows a selective decrease in complex II+III activity (z-score: -2.96). CONCLUSION Propofol impedes the electron flow through the respiratory chain and coenzyme Q is the main site of interaction with propofol.
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Research Support, Non-U.S. Gov't |
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Vanheel B, de Hemptinne A, Leusen I. Analysis of Cl- -HCO3(-) exchange during recovery from intracellular acidosis in cardiac Purkinje strands. THE AMERICAN JOURNAL OF PHYSIOLOGY 1984; 246:C391-400. [PMID: 6326603 DOI: 10.1152/ajpcell.1984.246.5.c391] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The possible role of a Cl- -HCO3(-) exchange mechanism in the recovery from intracellular acidosis of isolated cardiac Purkinje strands was investigated. Intracellular pH (pHi) was measured using double-barreled pH-sensitive microelectrodes. Acidifications were produced by withdrawing 20 meq NH+4 from the superfusate. Experiments were performed in normal CO2-HCO3(-)-buffered, in HCO3(-)free, and in Cl-free solutions and also in the presence of 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), a blocker of Cl--HCO3(-) exchange. In the absence of external HCO3(-), the apparent rate of acid extrusion following induced acidification was only slightly decreased, but the observed effect does not necessarily imply the intervention of a Cl--HCO3(-) exchange mechanism. SITS had little effect on the response to acidification. In zero-Cl- solutions, recovery of pHi from acidosis was not impaired. These observations suggest that in Purkinje fibers, [Cl-]i-[HCO3(-)]o exchange plays no significant role in recovery from intracellular acidification. Moreover, additional evidence is presented in favor of a passive HCO3(-) efflux at steady-state pHi in the normal superfusate. The apparent membrane permeability to HCO-3 was estimated to be 3.2 X 10(-8) cm X s-1.
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Vanheel B, Van de Voorde J, Leusen I. Contribution of nitric oxide to the endothelium-dependent hyperpolarization in rat aorta. J Physiol 1994; 475:277-84. [PMID: 8021834 PMCID: PMC1160377 DOI: 10.1113/jphysiol.1994.sp020068] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
1. The effect of endogenous and exogenous nitric oxide on the membrane potential (Em) of smooth muscle cells of the thoracic aorta of rats was investigated. 2. In tissues with intact endothelium, application of ACh or carbachol generated a change of the membrane potential consisting of an initial hyperpolarization by 10-12 mV, followed by a partial recovery toward a level which was at 10 min still 6-8 mV more negative than in control conditions. 3. Application of NG-nitro-L-arginine methylester (L-NAME), an inhibitor of endogenous NO production, had no significant effect on the resting membrane potential. The initial peak endothelium-dependent hyperpolarization elicited by ACh or carbachol was not significantly diminished. However, the recovery was more accentuated. Similarly, NG-monomethyl-L-arginine (L-NMMA) significantly diminished the second component of the endothelium-dependent hyperpolarization without affecting the magnitude of the first transient peak Em change. 4. Nitroglycerin produced a small sustained hyperpolarization of 1-2 mV, and the NO donor SIN-1, the active metabolite of molsidomine, similarly increased Em by about 1 mV. Infusion of high doses of acidified NaNO2 solution caused a hyperpolarization smaller than that evoked by ACh or carbachol. 5. 8-Bromo-cyclic GMP caused little change of membrane potential. In the presence of 8-Br-cGMP, ACh evoked a membrane electrical response similar to that observed in the absence of the nucleotide. 6. It is concluded that, in the rat aorta, the initial peak endothelium-dependent hyperpolarization observed under the influence of ACh or carbachol is not directly related to the synthesis of NO.(ABSTRACT TRUNCATED AT 250 WORDS)
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Vanheel B, de Hemptinne A, Leusen I. Influence of surface pH on intracellular pH regulation in cardiac and skeletal muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1986; 250:C748-60. [PMID: 3085512 DOI: 10.1152/ajpcell.1986.250.5.c748] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The influence of the surface pH (pHs) on the intracellular pH (pHi) and the recovery of pHi after an imposed intracellular acid load was investigated in isolated sheep cardiac Purkinje fiber, rabbit papillary muscle, and mouse and rat soleus muscle. pHs and pHi, respectively, were continuously measured by use of single- and double-barreled pH-sensitive glass microelectrodes. Surface acidosis, usually obtained by superfusion with solutions of acid pH, was also produced with low buffered (5 mM N-2-hydroxyethylpiperazine-N'-2-ethane-sulfonic acid) solutions at control pH. The pHs decrease (delta pHs) induced by low buffering was smallest (-0.08 pH unit) in Purkinje fiber and largest (-0.31 pH unit) in rat soleus muscle, which already had a more acid surface in control conditions. delta pHs was somewhat dependent on the superfusion rate. Higher superfusion rates decreased but did not abolish delta pHs. Surface acidosis was associated with a small intracellular acidification. Intracellular acid loads were produced by adding and subsequently withdrawing 20 meq/l NH4+ from the superfusate. In all preparations, the rate of recovery of pHi after NH4+ withdrawal was notably decreased at acidified pHs. This effect was amiloride sensitive. It is concluded that, in superfused multi-cellular preparations, pHs and therefore the buffer concentration of a superfusate can considerably influence steady-state pHi and pHi recovery from an imposed intracellular acid load.
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de Hemptinne A, Marrannes R, Vanheel B. Surface pH and the control of intracellular pH in cardiac and skeletal muscle. Can J Physiol Pharmacol 1987; 65:970-7. [PMID: 3304590 DOI: 10.1139/y87-154] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Both surface pH (pHs) and intracellular pH (pHi) were measured using single- and double-barreled pH-sensitive microelectrodes in isolated sheep cardiac Purkinje strands, rabbit and cat papillary muscle, and mouse and rat soleus muscle. Superfusion of the preparations with a relatively low buffered solution (containing 5 mM HEPES buffered to control pH) causes surface acidosis that correlates with efflux of metabolically produced acids in the unstirred layer of fluid surrounding the tissue. Acidification of the surface layer induces a slower acid change of pHi and depresses the rate of proton extrusion following an imposed intracellular acid load. In cardiac preparations, the lowering of pHi correlates with depression of twitch tension. Transient changes of pHs and pHi are seen when a weak acid or base is suddenly added to, or removed from the superfusion solution. Indirect evidence of the presence of carbonic anhydrase in the extracellular surface layer is obtained from analysis of transient pHs changes in presence and absence of acetazolamide.
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Review |
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Van den Bossche I, Vanheel B. Influence of cannabinoids on the delayed rectifier in freshly dissociated smooth muscle cells of the rat aorta. Br J Pharmacol 2000; 131:85-93. [PMID: 10960073 PMCID: PMC1572286 DOI: 10.1038/sj.bjp.0703521] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The influence of the cannabinoids anandamide, methanandamide and WIN 55212-2 on the delayed rectifier K(+) current (I(K(V))) in rat arterial myocytes was investigated. Anandamide caused a concentration-dependent reduction of total peak and late K(+) current (I(K)). The maximal effect (about 50% inhibition of I(K)) was reached with 3 microM, and half-maximal current block was observed at 0.6 microM. Blockade was voltage-independent. Inhibition of I(K) by the cannabinoid was associated with a characteristic increase in the rate of current relaxation. Methanandamide (10 microM), a metabolically more stable analogue of anandamide, decreased I(K) with a similar time course. Current traces in the presence of the drug also showed an acceleration of inactivation. The presence of TEA did not impair the inhibition by anandamide or methanandamide, but inhibition was prevented by pre-exposure to 4-AP, showing that both cannabinoids inhibited I(K(V)) while having no influence on Ca(2+)-dependent K(+) current (I(K(Ca))). The CB(1) receptor antagonist SR141716A (10 microM) did not influence the action of anandamide or methanandamide. Arachidonic acid (1 microM) increased I(K) considerably. However, in the presence of TEA it caused a decrease of I(K(V)) with a characteristic increase in the rate of current relaxation. WIN 55212-2 (20 microM) caused similar inhibition of I(K). Internally applied anandamide (10 microM) or methanandamide (10 microM) was ineffective at influencing I(K). In the dialyzed cells, the additional external application of a cannabinoid promptly initiated inhibition. The results show that anandamide, methanandamide and WIN 55212-2 affect I(K(V)) in a cannabinoid receptor-independent way similar to that of arachidonic acid, which, unlike the cannabinoids, additionally increases a Ca(2+)-activated K(+) current. It is suggested that cannabinoids might bind to an external site on or near the K(v) channel of the vascular smooth muscle cells.
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Bol M, Wang N, De Bock M, Wacquier B, Decrock E, Gadicherla A, Decaluwé K, Vanheel B, van Rijen HVM, Krysko DV, Bultynck G, Dupont G, Van de Voorde J, Leybaert L. At the cross-point of connexins, calcium, and ATP: blocking hemichannels inhibits vasoconstriction of rat small mesenteric arteries. Cardiovasc Res 2017; 113:195-206. [PMID: 27677282 DOI: 10.1093/cvr/cvw215] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 09/22/2016] [Accepted: 09/25/2016] [Indexed: 02/07/2023] Open
Abstract
AIMS Connexins form gap-junctions (GJs) that directly connect cells, thereby coordinating vascular cell function and controlling vessel diameter and blood flow. GJs are composed of two hemichannels contributed by each of the connecting cells. Hemichannels also exist as non-junctional channels that, when open, lead to the entry/loss of ions and the escape of ATP. Here we investigated cross-talk between hemichannels and Ca2+/purinergic signalling in controlling blood vessel contraction. We hypothesized that hemichannel Ca2+ entry and ATP release contributes to smooth muscle cell (SMC) Ca2+ dynamics, thereby influencing vessel contractility. We applied several peptide modulators of hemichannel function and inhibitors of Ca2+ and ATP signalling to investigate their influence on SMC Ca2+ dynamics and vessel contractility. METHODS AND RESULTS Confocal Ca2+ imaging studies on small mesenteric arteries (SMAs) from rat demonstrated that norepinephrine-induced SMC Ca2+ oscillations were inhibited by blocking IP3 receptors with xestospongin-C and by interfering with hemichannel function, most notably by the specific Cx43 hemichannel blocking peptide TAT-L2 and by TAT-CT9 that promotes Cx43 hemichannel opening. Evidence for hemichannel involvement in SMC function was supported by the fact that TAT-CT9 significantly increased SMC resting cytoplasmic Ca2+ concentration, indicating it facilitated Ca2+ entry, and by the observation that norepinephrine-triggered vessel ATP release was blocked by TAT-L2. Myograph tension measurements on isolated SMAs showed significant inhibition of norepinephrine-triggered contractility by the ATP receptor antagonist suramin, but the strongest effect was observed with TAT-L2 that gave ∼80% inhibition at 37 °C. TAT-L2 inhibition of vessel contraction was significantly reduced in conditional Cx43 knockout animals, indicating the effect was Cx43 hemichannel-dependent. Computational modelling suggested these results could be explained by the opening of a single hemichannel per SMC. CONCLUSIONS These results indicate that Cx43 hemichannels contribute to SMC Ca2+ dynamics and contractility, by facilitating Ca2+ entry, ATP release, and purinergic signalling.
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MESH Headings
- Adenosine Triphosphate/metabolism
- Animals
- Calcium/metabolism
- Calcium Signaling/drug effects
- Cell Communication/drug effects
- Computer Simulation
- Connexin 43/antagonists & inhibitors
- Connexin 43/deficiency
- Connexin 43/genetics
- Connexin 43/metabolism
- Connexins/antagonists & inhibitors
- Connexins/metabolism
- Female
- Gap Junctions/drug effects
- Gap Junctions/metabolism
- Genotype
- In Vitro Techniques
- Inositol 1,4,5-Trisphosphate Receptors/agonists
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Mesenteric Arteries/drug effects
- Mesenteric Arteries/metabolism
- Mice, Knockout
- Microscopy, Confocal
- Models, Cardiovascular
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Norepinephrine/pharmacology
- Peptides/pharmacology
- Phenotype
- Purinergic Antagonists/pharmacology
- Rats, Wistar
- Time Factors
- Vasoconstriction/drug effects
- Vasoconstrictor Agents/pharmacology
- Vasodilator Agents/pharmacology
- Gap Junction alpha-4 Protein
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Van de Voorde J, Vanheel B. Influence of cytochrome P-450 inhibitors on endothelium-dependent nitro-L-arginine-resistant relaxation and cromakalim-induced relaxation in rat mesenteric arteries. J Cardiovasc Pharmacol 1997; 29:827-32. [PMID: 9234666 DOI: 10.1097/00005344-199706000-00018] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In several blood vessels, endothelium-dependent vasorelaxation is in part mediated by an endothelium-derived hyperpolarizing factor (EDHF), the nature of which is as yet unknown. However, some evidence suggests that EDHF might be a cytochrome P-450-dependent monooxygenase metabolite of arachidonic acid. By using isometric tension measurements on rat main mesenteric arteries, the influence of four structurally and mechanistically different cytochrome P-450 inhibitors (proadifen, miconazole, 1-amino-benzotriazole, and 17-octadecynoic acid) was investigated on relaxations elicited by EDHF, assessed as the nitro-L-arginine-resistant component of acetylcholine-induced relaxation, and on relaxations provoked by the endothelium-independent potassium channel opener cromakalim. Proadifen (30 microM) inhibited the EDHF- as well as the cromakalim-induced relaxation, but not that elicited by nitroprusside. Also miconazole (30 microM) inhibited both the EDHF and the cromakalim-induced relaxation. On the other hand, 17-octadecynoic acid (5 microM) had no influence, and 1-aminobenzotriazole (1 mM) even potentiated EDHF- and cromakalim-induced relaxations. We conclude that the EDHF, released from the rat mesenteric artery by acetylcholine, is unlikely to be a cytochrome P-450-dependent monooxygenase metabolite of arachidonic acid and that proadifen and miconazole interfere with the action of cromakalim.
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Vanheel B, Leybaert L, De Hemptinne A, Leusen I. Simulated ischemia and intracellular pH in isolated ventricular muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1989; 257:C365-76. [PMID: 2764096 DOI: 10.1152/ajpcell.1989.257.2.c365] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Isolated guinea pig papillary muscles were subjected to an in vitro model of ischemia, consisting of superfusion arrest and immersion in paraffin oil, which results in restriction of substrate supply and metabolite washout. Intracellular pH (pHi) and surface pH (pHs) were measured with glass microelectrodes. Contractile force declined to 82% of the pre-"ischemic" value after 2 min and to 37% of the control value after 10 min. In addition, a shortening of the time to peak and duration of contraction was noted. The rate of force development decreased later than the rate of relaxation. After 10 min, pHi was acidified on average 0.08 pH unit, which is about one-third of the measured pHs change. Tripling the ischemic pHi change by reduction of the intracellular buffering power only slightly increased the rate of tension decline. Experimental pHi changes of similar magnitude, induced during normal superfusion, had a smaller effect on contractile force and failed to reproduce the characteristic changes in time course of the contraction. It is concluded that, in our condition of simulated ischemia, the intracellular acidification cannot account fully for the rapid decline in contractility.
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Van de Voorde J, Vanheel B, Leusen I. Depressed endothelium-dependent relaxation in hypertension: relation to increased blood pressure and reversibility. Pflugers Arch 1988; 411:500-4. [PMID: 3387186 DOI: 10.1007/bf00582370] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Endothelium-dependent relaxation effects have been reported to be impaired in thoracic aorta from genetic and experimentally induced hypertensive rats. This study extends these observations to carotid artery and abdominal aorta from renovascular hypertensive rats. It was also found that rats with coarctation of aorta show depressed endothelium-dependent relaxation responses in thoracic aorta above the stenosis (high pressure region) while no depressed responses are observed in abdominal aorta below the stenosis (normal pressure region). Reversibility of the depression of endothelium-dependent relaxation was investigated on aorta from renovascular hypertensive rats in which blood pressure was normalized by removal of the stenotic kidney three months after induction of hypertension. Endothelium-dependent responses were restored partially after 1-2 weeks and completely after two months of normalization of blood pressure. These results indicate that the increased blood pressure is indeed the causative factor responsible for the impaired endothelium-dependent relaxations in arteries from experimental hypertensive rats, a phenomenon which is reversible, at least in our experimental conditions.
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Vanheel B, de Hemptinne A. Influence of KATP channel modulation on net potassium efflux from ischaemic mammalian cardiac tissue. Cardiovasc Res 1992; 26:1030-9. [PMID: 1291079 DOI: 10.1093/cvr/26.11.1030] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
OBJECTIVE The aim was to investigate the effect of pre-exposure to inhibitors or activators of the ATP regulated K+ (KATP) channels on the ischaemia induced early changes of the extracellular K+ concentration, the extracellular pH, and the action potential in mammalian cardiac tissue. METHODS An in vitro model simulating ischaemia was applied to isolated guinea pig papillary muscles while simultaneous microelectrode measurements of the transmembrane potentials and of the pH and K+ activity at the surface of the preparation (pHs and asK respectively) were made. RESULTS During conditions of superfusion arrest, when accumulation of metabolic acids causes acidification of pHs, the simultaneous development of a true hypoxic state of the muscle is required in order to induce shortening of the action potential duration and accumulation of extracellular K+ with associated membrane depolarisation. Glibenclamide (10-50 microM) slowed the decrease of the action potential duration in 50% of the muscles, while the increase of asK was only moderately (approximately 20%) influenced. In the presence of 200 microM of the KATP channel inhibitor, the mean K+ accumulation was not significantly different from the control. The presence of tolbutamide (1 mM) had no effect on the decrease of action potential duration, but moderately slowed the increase of asK. Superfusion with lemakalim (BRL 38227) decreased action potential duration dose dependently. In papillary muscles in which action potential duration was shortened to approximately 60% of the control duration by presuperfusion with lemakalim, a subsequent ischaemic episode did not increase but rather delayed the rise in asK. During simulated ischaemia in the presence of Ba2+ ions (1 mM), asK showed a transient decrease followed by a rise at a rate similar to that in the absence of Ba2+. CONCLUSIONS Early ischaemic K+ accumulation and surface acidification are relatively insensitive to KATP channel inhibition or activation prior to the ischaemic insult. The rather loose coupling of the increase of asK and the decrease of action potential duration, as well as the limited effect of sulphonylureas on the K+ increase, suggests that mechanisms other than KATP channel opening could possibly contribute to the initial phase of ischaemic K+ accumulation.
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Vanheel B, de Hemptinne A, Leusen I. Intracellular pH and contraction of isolated rabbit and cat papillary muscle: effect of superfusate buffering. J Mol Cell Cardiol 1985; 17:23-9. [PMID: 3989871 DOI: 10.1016/s0022-2828(85)80089-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The influence of external buffering on surface pH (pHs), intracellular pH (pHi) and developed twitch tension was investigated in rabbit and cat papillary muscle. pHs and pHi were measured using single and double-barreled microelectrodes respectively. In 20 mM HEPES buffered solution, steady state pHi is close to that in control CO2/HCO-3 (25 mM HCO-3, 5% CO2) solution. pHs and developed tension also do not differ greatly from their control values. Decreasing the HEPES concentration to 5 mM, at constant external pH, lowers pHs considerably. The surface acidosis is associated with a small intracellular acidification; steady state pHi in 5 mM HEPES is always more acid than that in control CO2/HCO-3. A significant decrease in developed tension is also seen in 5 mM HEPES. Alteration of the superfusion velocity influences pHs only slightly. Stimulation of the muscle at high frequency is shown to increase surface acidification, the extent of which is dependent on the buffer concentration. The conclusion from the present experiments is that in papillary muscle external buffering influences intracellular pH and contraction via its effect on pHs.
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Javaheri S, De Hemptinne A, Vanheel B, Leusen I. Changes in brain ECF pH during metabolic acidosis and alkalosis: a microelectrode study. JOURNAL OF APPLIED PHYSIOLOGY: RESPIRATORY, ENVIRONMENTAL AND EXERCISE PHYSIOLOGY 1983; 55:1849-53. [PMID: 6420378 DOI: 10.1152/jappl.1983.55.6.1849] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We used pH-sensitive double-barreled microelectrodes to measure brain extracellular fluid (ECF) pH in anesthetized dogs during isocapnic infusion acidosis (HCl) and alkalosis (Na2CO3) of 45-60 min duration. The diameter of the tips of these electrodes varied from less than 1 to 27 micron and were placed 5 mm below the surface of the parietal cortex. In group I (metabolic acidosis, n = 5) mean plasma and brain ECF pH fell significantly by 0.221 and 0.025, respectively, with changes in brain ECF pH being 11.3% of those noted in plasma. In group II (metabolic alkalosis, n = 5) mean plasma and brain ECF pH rose significantly by 0.170 and 0.049, respectively, with changes in brain ECF pH being 28.8% of those noted in plasma. Mean arterial and sagittal venous PCO2 and cisternal cerebrospinal fluid (CSF) acid-base variables did not change significantly during acid or base infusion. We conclude that during transients of isocapnic metabolic acid-base perturbations ionic gradients exist between brain ECF and CSF and that changes in brain ECF pH measured by microelectrodes follow the changes in plasma pH. These pH changes may play an important role in respiratory adaptations of acute metabolic acidosis and alkalosis.
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Van de Voorde J, Vanheel B. EDHF-mediated relaxation in rat gastric small arteries: influence of ouabain/Ba2+ and relation to potassium ions. J Cardiovasc Pharmacol 2000; 35:543-8. [PMID: 10774783 DOI: 10.1097/00005344-200004000-00005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In several blood vessels, endothelium-dependent vasorelaxation is in part mediated by an endothelium-derived hyperpolarizing factor (EDHF), the nature of which is as yet unknown. Experiments were performed to investigate whether the recently raised hypothesis that EDHF might be identified as the potassium ion, released by activation of endothelial K(Ca) channels and inducing relaxation by stimulation of Na+/K+-pump and the inward rectifier K+ conductance, might be valid for small rat gastric arteries. EDHF-induced relaxation (assessed as the nitro-L-arginine/indomethacin resistant component of acetylcholine-induced relaxation), but not nitroprus-side-induced relaxation is strongly inhibited in the presence of ouabain (0.5 mM)/Ba2+ (30 microM), ouabain being responsible for the greater part of the inhibition. This inhibition is reversible. Application of increasing concentrations of K+ elicits transient relaxations in some preparations, but in a greater part of the preparations, no or only small relaxations. In membrane potential measurements, it was found that increasing concentrations of extracellular K+ consistently depolarized smooth muscle cells, whereas acetylcholine elicits hyperpolarization. The K(Ca) channel openers NS 1619 and 1-EBIO elicit relaxation effects that are not diminished after removal of the endothelium and are not inhibited by ouabain/Ba2+. It is concluded that EDHF-mediated relaxation is sensitive to inhibition by ouabain/Ba2+, but that the relation of this inhibitory influence to an action of K+ as EDHF is uncertain.
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Van de Voorde J, Delaey C, Depypere H, Vanheel B. Mechanisms involved in the vasorelaxing influence of histamine on isolated human subcutaneous resistance arteries. Eur J Pharmacol 1998; 349:61-6. [PMID: 9669497 DOI: 10.1016/s0014-2999(98)00179-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The effects of histamine were analysed on human subcutaneous small arteries. No effect was seen on non-precontracted preparations. After precontraction (norepinephrine 1 microM and K+ 30 mM) histamine potently relaxed the arteries (EC50 = 0.3 microM; max. effect = 95% relaxation). The histamine H1 receptor antagonist, pyrilamine (10 microM), had only a small, non-significant inhibitory influence on histamine-induced relaxation while the histamine H2 receptor antagonist, cimetidine (0.1 mM), had a significant inhibitory influence. Relaxation was completely blocked in the presence of both antagonists. Both 2-pyridylethylamine (histamine H1 receptor agonist) and dimaprit (histamine H2 receptor agonist) elicited relaxation. Removal of endothelium reduced the relaxation effects of histamine and 2-pyridylethylamine, but not of dimaprit. Inhibition of nitric oxide synthesis by nitro-L-arginine significantly inhibited histamine-induced relaxation and even more clearly the cimetidine-resistant component. We conclude that histamine potently relaxes human subcutaneous arterioles, and that most probably both muscular histamine H2 receptors and endothelial histamine H1 receptors, thus activating nitric oxide release, contribute to the relaxation.
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Vanheel B, de Hemptinne A, Leusen I. Acidification and intracellular sodium ion activity during stimulated myocardial ischemia. THE AMERICAN JOURNAL OF PHYSIOLOGY 1990; 259:C169-79. [PMID: 2164781 DOI: 10.1152/ajpcell.1990.259.1.c169] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
With the use of microelectrodes, intracellular pH (pHi), surface pH (pHs), and intracellular Na+ activity (aiNa) were measured in isolated guinea pig papillary muscles during normal superfusion and during a reversible condition of simulated ischemia. Acid loading by NH+4 prepulse or by CO2-HCO3- addition during superfusion with pH 7.4 solutions caused internal acidification followed by a recovery of pHi, which could be inhibited by amiloride. pHi recovery was associated with an amiloride-sensitive peak rise of aiNa and membrane hyperpolarization, indicative of Na(+)-H+ exchange. Peak increase of aiNa was absent if the pH of the superfusion solution was concomitantly lowered. Imposed ischemia after control superfusion caused membrane depolarization and acidification of pHi and pHs. The change of pHs consistently was larger than that of pHi. aiNa decreased from 5.5 to 4.6 mM after 10-min ischemia. Enlarging the pHi (and pHs) decrease in ischemia by prior reduction of the tissue buffer capacity (CO2-HCO3(-)-free superfusion) was unable to induce a rise of aiNa during the subsequent ischemic period. Amiloride had no significant effect on aiNa during ischemia. It is concluded that the important acidification of pHs reduces the rate of pHi regulatory Na(+)-H+ exchange and thereby contributes to a longer maintenance of the Na+ electrochemical gradient in ischemic cardiac muscle.
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Van de Voorde J, Brochez V, Vanheel B. Heterogenous effects of histamine on isolated rat coronary arteries. Eur J Pharmacol 1994; 271:17-23. [PMID: 7535230 DOI: 10.1016/0014-2999(94)90259-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The influence of increasing concentrations of histamine (0.1 microM-1 mM) was studied on proximal and distal ring segments of left anterior descendens coronary arteries isolated from rats. Addition of histamine to prostaglandin F2 alpha (10 microM)-precontracted proximal segments elicited a further contraction. This effect was endothelium-independent and mediated by a histamine H1 receptor mechanism since it was blocked by the histamine H1 receptor antagonist, mepyramine (10 microM), and not by the histamine H2 receptor antagonist, cimetidine (100 microM), and since it was mimicked by the histamine H1 receptor agonist, 2-pyridylethylamine, and not by the histamine H2 receptor agonist, dimaprit. Addition of histamine to prostaglandin F2 alpha-precontracted distal segments elicited concentration-dependent relaxation. This relaxation is histamine H2 receptor-mediated since it was blocked by cimetidine (100 microM) and not by mepyramine (10 microM) and since dimaprit but not 2-pyridylethylamine elicited relaxation. The relaxation was not due to the release of endothelial NO, prostaglandins or activation of ATP-regulated K+ channels since it was not inhibited by NG-nitro-L-arginine methyl ester (100 microM) or NG-nitro-L-arginine (100 microM), indomethacin (10 microM) or glibenclamide (10 microM). Our results show that the effects of histamine on rat left anterior descendens coronary arteries are heterogenous, depending on the relative location within the coronary vasculature and possibly, the relative preponderance of histamine H1 or H2 receptors on the smooth muscle cells.
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Breyne J, Vanheel B. Methanandamide hyperpolarizes gastric arteries by stimulation of TRPV1 receptors on perivascular CGRP containing nerves. J Cardiovasc Pharmacol 2006; 47:303-9. [PMID: 16495770 DOI: 10.1097/01.fjc.0000205053.53946.10] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Endogenous as well as synthetic cannabinoids have potent vasodilatory actions in a variety of vascular preparations. Their precise mechanism of action is as yet unclear, but several studies point to the activation of type 1 vanilloid (TRPV1) receptors on primary afferent perivascular nerves, stimulating the release of calcitonin gene related peptide (CGRP). Given the documented gastroprotective function of these nerves, and the various gastrointestinal effects reported for cannabinoids, we explored a possible link between these systems in the gastric circulation by comparing responses of small gastric arteries to cannabinoids and to calcitonin gene related peptide using conventional microelectrode techniques. Exposure of small gastric arteries to the stable endocannabinoid analogue methanandamide caused a hyperpolarization of the vascular smooth muscle cells, which was completely abolished by the vanilloid receptor antagonist capsazepine (P < 0.01). Exposure to exogenous calcitonin gene related peptide evoked fully reproducible (P > 0.05) hyperpolarizations with similar time course, unaffected by capsazepine. Preincubation with glibenclamide, an inhibitor of ATP-sensitive potassium (KATP) channels, reversed both responses to methanandamide (P < 0.01) and calcitonin gene related peptide (P < 0.05). Similar results were found in rat mesenteric arteries. These findings show that cannabinoids stimulate TRPV1 receptors, presumably causing the release of calcitonin gene related peptide, which hyperpolarizes the smooth muscle cells by activation of KATP channels. Because membrane hyperpolarization is a powerful mediator of vasorelaxation, this novel pathway might prove to be an important mechanism affording gastroprotection.
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Vanheel B, Vandeputte-Poma J, Desmeth M. Resorption of yolk lipids by the pigeon embryo. ACTA ACUST UNITED AC 1981. [DOI: 10.1016/0300-9629(81)90371-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Vanheel B, Calders P, Van den Bossche I, Van de Voorde J. Influence of some phospholipase A2 and cytochrome P450 inhibitors on rat arterial smooth muscle K+ currents. Can J Physiol Pharmacol 1999. [DOI: 10.1139/y99-050] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The hyperpolarizing factor that is liberated by vascular endothelial cells in response to various agonists, and known to induce relaxation by opening of smooth muscle K+ channels, has been suggested to be a product of cytochrome P450 dependent arachidonic acid metabolism. In this study, the direct influence of two phospholipase A2 inhibitors and of five structurally and mechanistically different cytochrome P450 inhibitors on K+ currents in freshly isolated vascular smooth muscle cells from the rat aorta was investigated. On stepping the cell membrane potential from -70 mV to a series of depolarized test potentials, a noisy outward current developed at test potentials > +10 mV, which showed no appreciable inactivation during the voltage pulse. It was largely abolished by 3 mM external tetraethylammonium chloride (TEA), suggesting that it predominantly consisted of current through large-conductance Ca2+-activated K+ channels. The phospholipase A2 inhibitor quinacrine considerably inhibited this TEA-sensitive current, while 4-bromophenacylbromide exerted no effect. The cytochrome P450 inhibitors proadifen and miconazole reversibly decreased the amplitude of IK, while clotrimazole and 1-aminobenzotriazole had no effect. Conversely, 17-octadecynoic acid increased whole-cell IK. These results show that some phospholipase A2 and cytochrome P450 inhibitors may interfere with K+ channel activation in the rat arterial smooth muscle cell. The relevance of these findings to studies on the involvement of cytochrome P450 dependent metabolism in the generation of the endothelium-derived hyperpolarizing factor in intact arteries is discussed.Key words: endothelial factors, smooth muscle, membrane currents, vasodilation, endothelium-derived hyperpolarizing factor (EDHF), arachidonic acid.
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