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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Angiotensin II (Ang II) is a potent vasoconstrictor in the peripheral circulation and has been implicated in many cardiovascular diseases associated with elevated oxidative stress. However, its direct vasomotor action and its linkage to oxidative stress-induced vascular dysfunction in the coronary microcirculation remain elusive. In this study, we directly assessed the vasomotor action of Ang II in isolated porcine coronary arterioles and also examined whether Ang II can modulate endothelium-dependent nitric oxide (NO)-mediated dilation via superoxide production. Ang II evoked vasoconstriction at a low concentration (1 nmol/L) and dilations at higher concentrations (>10 nmol/L). Ang II type 1 (AT(1)) receptor antagonist losartan abolished vasoconstriction, whereas Ang II type 2 (AT(2)) receptor antagonist PD 123319 eliminated vasodilation. Adenosine stimulated a significant arteriolar NO production and dilation. NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) abolished stimulated NO production and attenuated vasodilation. Pretreating vessels with a subvasomotor concentration of Ang II (0.1 nmol/L, 60 minutes) mimicked inhibitory effects of L-NMMA. Ang II-mediated inhibition was not observed in the presence of L-NMMA or after endothelial removal but was prevented by losartan, superoxide scavenger TEMPOL, or NADPH oxidase inhibitor apocynin. Dihydroethidium staining showed that Ang II elicited losartan- and TEMPOL-sensitive superoxide production in arterioles. These results demonstrate that Ang II evokes AT1 receptor-mediated vasoconstriction and AT2 receptor-mediated vasodilation of coronary arterioles. Ang II at a subvasomotor level impairs endothelium-dependent NO-mediated dilation attributable to elevated superoxide production via AT1 receptor activation of NADPH oxidase. These data may partly explain the impaired coronary flow regulation in heart diseases associated with an upregulated renin-angiotensin system.
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PMID:Divergent roles of angiotensin II AT1 and AT2 receptors in modulating coronary microvascular function. 1259 45

Adenosine is a purine nucleoside that regulates cell function through G protein-coupled receptors that activate or inhibit adenylyl cyclase. Based on the understanding that cAMP regulates alveolar epithelial active Na(+) transport, we hypothesized that adenosine and its receptors have the potential to regulate alveolar ion transport and airspace fluid content. Herein, we report that type 1 (A(1)R), 2a (A(2a)R), 2b (A(2b)R), and 3 (A(3)R) adenosine receptors are present in rat and mouse lungs and alveolar type 1 and 2 epithelial cells (AT1 and AT2). Rat AT2 cells generated and produced cAMP in response to adenosine, and micromolar concentrations of adenosine were measured in bronchoalveolar lavage fluid from mice. Ussing chamber studies of rat AT2 cells indicated that adenosine affects ion transport through engagement of A(1)R, A(2a)R, and/or A(3)R through a mechanism that increases CFTR and amiloride-sensitive channel function. Intratracheal instillation of low concentrations of adenosine (< or =10(-8)M) or either A(2a)R- or A(3)R-specific agonists increased alveolar fluid clearance (AFC), whereas physiologic concentrations of adenosine (> or =10(-6)M) reduced AFC in mice and rats via an A(1)R-dependent pathway. Instillation of a CFTR inhibitor (CFTR(inh-172)) attenuated adenosine-mediated down-regulation of AFC, suggesting that adenosine causes Cl(-) efflux by means of CFTR. These studies report a role for adenosine in regulation of alveolar ion transport and fluid clearance. These findings suggest that physiologic concentrations of adenosine allow the alveolar epithelium to counterbalance active Na(+) absorption with Cl(-) efflux through engagement of the A(1)R and raise the possibility that adenosine receptor ligands can be used to treat pulmonary edema.
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PMID:Adenosine regulation of alveolar fluid clearance. 1736 Apr 81

Adenosine is an endogenously purine nucleoside which plays a significant role in regulation of airways tone and reactivity by multiple and incompletely known mechanisms, including the release of endogenously active peptides from mast cells via activation of the A3 receptors. Our previous results suggested that releasing of enzymes from activated mast cells could activate the intrapulmonary renin angiotensin system (RAS). In this study, we investigated the involvement of angiotensin II (Ang II) in adenosine-induced bronchoconstriction in an experimental model of allergic asthma. On bronchial rings from ovalbumin (OVA) sensitized rats, after in vitro challenge, adenosine induced small contractile effects which became significant after indomethacin pre-treatment. On the other hand adenosine pre-treatment amplified bronchoconstriction induced by the allergen (OVA) challenge and reduced bronchial relaxation of acetylcholine pre-contracted bronchial rings by cumulative doses of terbutaline. All these effects are significantly lower on rats treated with losartan (a blocker of Ang II type 1 specific receptors, AT1) in the last two weeks of sensitization protocol (50 mg/kg/day). Our data confirmed that adenosine induced bronchial hyperreactivity could be partially a result of RAS activation in abnormal conditions as antigen sensitization and challenge.
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PMID:[Involvement of angiotensin on adenosine-induced bronchial hyperreactivity]. 1950 82

The primary function of angiotensin II, the main peptide of central renin-angiotensin system (RAS), is regulation of blood pressure. Recently, new functions of so-called local (or tissue) RAS have been discovered in brain. AT1 and AT2 angiotensin receptors, found in many parts of central nervous system (CNS), stimulate various signalling pathways. Gamma-amniobutyric acid (GABA), which acts by three types of receptors, is the crucial inhibitory neurotransmitter. GABA and angiotensins are found in brain regions like paraventricular nucleus of hypothalamus, nucleus tractus solitari and rostral ventrolateral medulla, all involved in blood pressure regulation. The influence of angiotensin II on GABA action is different in various CNS regions, but mainly it is associated with cardiovascular neurons activity. There are other neurotransmitters which may interact with angiotensins action. Adenosine has inhibitory effect and play important role in epilepsy. Its beneficial influence may be stronger in presence of angiotensin. Angiotensins also interact with dopamine (DA) activity by stimulation of DA-synthesizing nerves.
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PMID:[Angiotensins as neuromodulators]. 2366 41

Adenosine 5-triphosphate (ATP) is the main free energy carrier in metabolism. In budding yeast, shifts to glucose-rich conditions cause dynamic changes in ATP levels, but it is unclear how heterogeneous these dynamics are at a single-cell level. Furthermore, pH also changes and affects readout of fluorescence-based biosensors for single-cell measurements. To measure ATP changes reliably in single yeast cells, we developed yAT1.03, an adapted version of the AT1.03 ATP biosensor, that is pH-insensitive. We show that pregrowth conditions largely affect ATP dynamics during transitions. Moreover, single-cell analyses showed a large variety in ATP responses, which implies large differences of glycolytic startup between individual cells. We found three clusters of dynamic responses, and we show that a small subpopulation of wild-type cells reached an imbalanced state during glycolytic startup, characterized by low ATP levels. These results confirm the need for new tools to study dynamic responses of individual cells in dynamic environments.
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PMID:An Improved ATP FRET Sensor For Yeast Shows Heterogeneity During Nutrient Transitions. 3207 76