0000000000088093
AUTHOR
M. Antonia Noguera
Evidence that depletion of internal calcium stores sensitive to noradrenaline elicits a contractile response dependent on extracellular calcium in rat aorta.
1. Noradrenaline 1 microM induced a contractile response in rat isolated aorta in the presence or in the absence of extracellular Ca2+ with depletion of intracellular Ca2+ stores. Thereafter, during incubation in the presence of Ca2+, an increase in the resting tone was observed. Such a contractile response did not occur after exposure to caffeine or 5-hydroxytryptamine. 2. This increase in tension was inhibited in a concentration-dependent manner by alpha-adrenoceptor antagonists (prazosin, phentolamine and yohimbine), the non-specific relaxing compound, papaverine and by the Ca(2+)-entry blocker, nifedipine. Therefore, this contractile process is related to depletion of Ca2+ stores sensit…
Modulatory role of magnesium on the contractile response of rat aorta to several agonists in normal and calcium-free medium.
Abstract Acute withdrawal of external Mg2+ increased basal tone of rat isolated aorta incubated in the presence of Ca2+. Above normal levels of Mg2+ (1–4 Mm) inhibited basal tone while much higher levels of the divalent cation (64–256 Mm) evoked contractile responses regardless of the presence of Ca2+. Contractile responses to noradrenaline (1μm) and KCl (80 Mm) were inhibited by addition of cumulative concentrations of Mg2+. Acetylcholine-induced contractions in the presence of physiological concentrations of Mg2+ (1 Mm) decreased gradually to the basal tone, but a sustained contraction was observed in the absence of this ion. In Ca2+-free medium, acetylcholine-induced phasic responses ind…
NT3/TrkC pathway modulates the expression of UCP-1 and adipocyte size in human and murine adipose tissue
ABSTRACTNT3, through activation of its tropomyosin-related kinase receptor C (TrkC), modulates neuronal survival and neural stem cell differentiation. It is widely distributed in peripheral tissues (specially vessels and pancreas) and this ubiquitous pattern suggests a role for NT3, outside the nervous system and related to metabolic functions. The presence of the NT3/TrkC pathway in the adipose tissue (AT) has never been investigated. Present work studies in human and murine adipose tissue (AT) the presence of elements of the NT3/TrkC pathway and its role on lipolysis and adipocyte differentiation. qRT-PCR and immunoblot indicate that NT3 was present in human retroperitoneal AT and decreas…
Pathological role of a constitutively active population of α1D -adrenoceptors in arteries of spontaneously hypertensive rats
The role of a constitutively active population of α1D-adrenoceptors was analysed in arteries obtained from spontaneously hypertensive rats (SHR) and controls (WKY) divided into three groups: young prehypertensive, adult hypertensive, and adult animals chronically treated with captopril (50 mg kg−1 per day orally) in order to prevent the hypertensive state. In adult SHR, a significant increase in BMY 7378 potency (not in prazosin potency) was observed in aorta, mesenteric artery, and the first and second branches of the small mesenteric arteries with respect to WKY rats. This difference was not observed in iliac and tail arteries, which suggests an increased functional role of α1D-adrenocept…
Changes in Adrenoceptors and G-Protein-Coupled Receptor Kinase 2 in <smlcap>L</smlcap>-NAME-Induced Hypertension Compared to Spontaneous Hypertension in Rats
This work compares the expression of adrenoceptors (ARs) and G-protein-coupled receptor kinase (GRK) 2 (RT-PCR and immunoblotting) and functional responses in conductance (aorta) and resistance vessels (mesenteric resistance arteries; MRA) in two different models of rat hypertension: hypertension induced by chronic treatment with <smlcap>L</smlcap>-NAME (N<sup>G</sup>-nitro-<smlcap>L</smlcap>-arginine methyl-ester) (<smlcap>L</smlcap>-NAME-treated rats; LNHR), and genetically induced hypertension (spontaneously hypertensive rats; SHR). Changes found in the aorta, but not in the MRA, were: (1) a loss of contractile capacity, more evidently in α…
Functional evidence of inverse agonism in vascular smooth muscle
1. In the present study, depletion of internal Ca2+ stores sensitive to noradrenaline (1 microM) in rat aorta, is the signal for the entry of extracellular Ca2+, not only to refill the stores but also, in our experimental conditions, to activate the contractile proteins. This induces an increase in the resting tone that constitutes, the first functional evidence of this Ca2+ entry. 2. The fact that methoxamine (100 microM) reproduces the same processes as noradrenaline but clonidine (1 microM) does not, indicates that alpha(1)-adrenoceptor activation is related to the increase in the resting tone observed after depletion of adrenoceptor-sensitive internal Ca2+-stores. 3. Benoxathian and WB …
Characterization of two different Ca2+ entry pathways dependent on depletion of internal Ca2+ pools in rat aorta
Ryanodine (10 microM), thapsigargin (1 microM) and cyclopiazonic acid (10 microM) produced a slow, sustained contractile response in rat aorta that only can be observed in Ca2+-containing solution. In Ca2+-free medium, no response to the drugs was obtained, which suggests that the contraction elicited in presence of Ca2+ is mainly due to the contribution of extracellular influx. This Ca2+ entry does not depend on the opening of dihydropyridine-dependent Ca2+-channels for nimodipine does not affect this. Noradrenaline (1 microM) induced a biphasic response in Ca2+-free medium that was mediated by two different Ca2+ compartments, one of which is common to caffeine (10 mM), and is also deplete…
Functional characterization of α1 -adrenoceptor subtypes in vascular tissues using different experimental approaches:a comparative study
The α1-adrenergic responses of rat aorta and tail artery have been analysed measuring the contractility and the inositol phosphate (IP) formation induced by noradrenaline. Three antagonists, prazosin, 5-methylurapidil (α1A selective) and BMY 7378 (α1D selective) have been used in different experimental procedures. Noradrenaline possesses a greater potency inducing contraction and IP accumulation in aorta (pEC50-contraction=7.32±0.04; pEC50-IPs=6.03±0.08) than in the tail artery (pEC50-contraction=5.71±0.07; pEC50-IPs=5.51±0.10). Although the maximum contraction was similar in both tissues (Emax-tail=619.1±55.6 mg; Emax-aorta-698.2±40.8 mg), there were marked differences in the ability of th…
Mechanism of the cardiovascular activity of laudanosine: comparison with papaverine and other benzylisoquinolines.
1. The activity of (+/-)-laudanosine, a benzyltetrahydroisoquinoline alkaloid, was investigated in pithed rats and rat isolated aorta. Its effects on [3H]-(+)-cis-diltiazem and [3H]-nitrendipine binding to rat cerebral cortical membranes, and on the different molecular forms of cyclic nucleotide phosphodiesterases (PDE) isolated from bovine aorta were investigated. 2. The dose-response curve to methoxamine (3-300 micrograms kg-1, i.v.) in normotensive pithed rats was shifted to the right by (+/-)-laudanosine, 3 and 6 mg kg-1. 3. (+/-)-Laudanosine inhibited in a concentration-dependent manner the contractile responses evoked by noradrenaline (NA 1 microM), depolarizing solution (KCl 80 mM) o…
8-NH2-Boldine, an Antagonist of α1Aand α1BAdrenoceptors without Affinity for the α1DSubtype: Structural Requirements for Aporphines at α1-Adrenoceptor Subtypes
Structure-activity analysis of 21 aporphine derivatives was performed by examining their affinities for cloned human alpha (1A), alpha (1B) and alpha (1D) adrenoceptors (AR) using membranes prepared from rat-1 fibroblasts stably expressing each alpha (1)-AR subtype. All the compounds tested competed for [ (125)I]-HEAT binding with steep and monophasic curves. The most interesting compound was 8-NH (2)-boldine, which retains the selective affinity for alpha(1A)-AR (pKi = 6.37 +/- 0.21) vs. alpha(1B)-AR (pKi = 5.53 +/- 0.11) exhibited by 1,2,9,10-tetraoxygenated aporphines, but shows low affinity for alpha(1D)-AR (pKi < 2.5). Binding studies on native adrenoceptors present in rat cerebral cor…
Opposite vascular activity of (R)-apomorphine and its oxidised derivatives. Endothelium-dependent vasoconstriction induced by the auto-oxidation metabolite
We have synthetised a series of oxidised apomorphine derivatives (orto and para quinones 2-5), in order to analyse their vascular activity. We have performed radioligand binding assays on rat cortical membranes and functional studies on rat aortic rings. Instead the relaxant activity exhibited by (R)-apomorphine, o-quinones 2, 4, show contractile activity dependent on endothelium in rat aortic rings. Compound 2, the main metabolite of (R)-apomorphine auto-oxidation, was the product which showed enhanced contractile activity by a complex mechanism related to activation of Ca(2+) channels through release and/or inhibition of endothelial factors. Moreover, this compound disrupts the endothelia…
The effect of S-(+)-boldine on the α1-adrenoceptor of the guinea-pig aorta
1. The cardiovascular activity of S-(+)-boldine, an aporphine alkaloid structurally related to papaverine, was determined. The work includes functional studies on guinea-pig isolated aorta contracted with noradrenaline, caffeine, KCl or Ca2+, and on guinea-pig trachea contracted with acetylcholine or histamine. 2. S-(+)-boldine inhibited in a concentration-dependent manner the contractile response evoked by noradrenaline (10 microM) in guinea-pig aorta (IC50 = 1.4 +/- 0.2 microM) while the KCl depolarizing solution (60 mM)- or the Ca2+ (1 mM)-induced contractions were only partially affected by boldine up to 300 microM. In contrast, papaverine relaxed noradrenaline (NA), KCl or Ca2+ induced…
Multiple actions of glaucine on cyclic nucleotide phosphodiesterases, α1-adrenoceptor and benzothiazepine binding site at the calcium channel
1. In the present study, the properties of glaucine (an aporphine structurally related to papaverine) were compared with those of papaverine, diltiazem, nifedipine and prazosin. The work includes functional studies on rat isolated aorta contracted with noradrenaline, caffeine or KCl, and a determination of the affinity of glaucine at calcium channel binding sites of alpha-adrenoceptors, by use of [3H]-(+)-cis-diltiazem, [3H]-nitrendipine and [3H]-prazosin binding to cerebral cortical membranes. The effects of glaucine on the different molecular forms of cyclic nucleotide phosphodiesterases (PDE) isolated from bovine aorta were also determined. 2. Contraction evoked by noradrenaline (1 micro…
Annexin A2-Mediated Plasminogen Activation in Endothelial Cells Contributes to the Proangiogenic Effect of Adenosine A2A Receptors
Adenosine A2A receptor mediates the promotion of wound healing and revascularization of injured tissue, in healthy and animals with impaired wound healing, through a mechanism depending upon tissue plasminogen activator (tPA), a component of the fibrinolytic system. In order to evaluate the contribution of plasmin generation in the proangiogenic effect of adenosine A2A receptor activation, we determined the expression and secretion of t-PA, urokinase plasminogen activator (uPA), plasminogen activator inhibitor-1 (PAI-1) and annexin A2 by human dermal microvascular endothelial cells stimulated by the selective agonist CGS-21680. The plasmin generation was assayed through an enzymatic assay a…