scholarly journals Adenosine signaling in outer medullary descending vasa recta

2001 ◽  
Vol 280 (3) ◽  
pp. R854-R861 ◽  
Author(s):  
Erik P. Silldorff ◽  
Thomas L. Pallone
Keyword(s):  
Calcium Ionophore ◽  
Receptor Activation ◽  
Calcium Ionophore A23187 ◽  
No Synthase ◽  
Ionophore A23187 ◽  
Ang Ii ◽  
Cytoplasmic Calcium ◽  
Camp Production ◽  
Camp Analog ◽  
Vasa Recta

We tested whether dilation of outer medullary descending vasa recta (OMDVR) is mediated by cAMP, nitric oxide (NO), and cyclooxygenase (COX). Adenosine (A; 10−6 M)-induced vasodilation of ANG II (10−9 M)-preconstricted OMDVR was mimicked by the cAMP analog 8-bromoadenosine 3′,5′-cyclic monophosphate (10−10to 10−4 M) and reversed by the adenylate cyclase inhibitor SQ-22536. Adenosine (10−4 M) stimulated OMDVR cAMP production greater than threefold. NO synthase blockade with N G-nitro-l-arginine methyl ester and N G-monomethyl-l-arginine (10−4 M) did not affect adenosine vasodilation. Adenosine induced endothelial cytoplasmic calcium transients that were small. Indomethacin (10−6 M) reversed adenonsine-induced dilation of OMDVR preconstricted with ANG II, endothelin, 4-bromo-calcium ionophore A23187, or carbocyclic thromboxane A2. In contrast, selective A2-receptor activation dilated endothelin-preconstricted OMDVR even in the presence of indomethacin. We conclude that OMDVR vasodilation by adenosine involves cAMP and COX but not NO. COX blockade does not fully inhibit selective A2 receptor-mediated OMDVR dilation.

Inhibitory Effects of Etomidate and Ketamine on Endothelium-dependent Relaxation in Canine Pulmonary Artery

2001 ◽  
Vol 94 (4) ◽  
pp. 668-677 ◽  
Author(s):  
Koji Ogawa ◽  
Satoru Tanaka ◽  
Paul A. Murray
Keyword(s):  
Pulmonary Artery ◽  
Calcium Ionophore ◽  
Receptor Activation ◽  
Isometric Tension ◽  
Calcium Ionophore A23187 ◽  
Ionophore A23187 ◽  
Inhibitory Effects ◽  
Pulmonary Arterial ◽  
Synthase Inhibitor ◽  
Endothelium Dependent Relaxation

Background The authors recently demonstrated that acetylcholine-induced pulmonary vasorelaxation had two primary components, nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF). The goal was to investigate the effects of etomidate and ketamine on the NO- and EDHF-mediated components of pulmonary vasorelaxation in response to acetylcholine, bradykinin, and the calcium ionophore, A23187. Methods Canine pulmonary arterial rings with an intact endothelium were suspended in organ chambers for isometric tension recording. The effects of etomidate and ketamine (10(-5) M and 10(-4) M) on vasorelaxation responses to acetylcholine, bradykinin, and A23187 were assessed in phenylephrine-contracted rings. The NO- and EDHF-mediated components of relaxation were assessed using a NO synthase inhibitor (N-nitro-L-arginine methylester [L-NAME]: 10(-4) M) and a Ca2+-activated potassium channel inhibitor (tetrabutylammonium hydrogen sulfate [TBA]: 10(-3) M) in rings pretreated with a cyclooxygenase inhibitor (ibuprofen: 10(-5) M). Intracellular calcium concentration ([Ca2+]i) was measured in cultured bovine pulmonary artery endothelial cells loaded with acetoxylmethyl ester of fura-2. Results Etomidate and ketamine attenuated pulmonary vasorelaxation in response to acetylcholine and bradykinin, whereas they had no effect on the response to A23187. The relaxant responses to acetylcholine and bradykinin were attenuated by L-NAME or TBA alone and were abolished by combined inhibition in rings pretreated with ibuprofen. Etomidate and ketamine further attenuated both L-NAME-resistant and TBA-resistant relaxation. These anesthetics also inhibited increases in endothelial [Ca2+]i in response to bradykinin, but not A23187. Conclusion These results indicate that etomidate and ketamine attenuated vasorelaxant responses to acetylcholine and bradykinin by inhibiting both NO- and EDHF-mediated components. Moreover, our results suggest that these anesthetics do not directly suppress NO or EDHF activity, but rather inhibit the endothelial [Ca2+]i transient in response to receptor activation.

Inhibitory Effect of Fentanyl on Acetylcholine-induced Relaxation in Rat Aorta

2004 ◽  
Vol 101 (1) ◽  
pp. 89-96 ◽  
Author(s):  
Ju-Tae Sohn ◽  
Seong-Ho Ok ◽  
Hee-Jin Kim ◽  
Seon-Hak Moon ◽  
Il-Woo Shin ◽  
...  
Keyword(s):  
Muscarinic Receptor ◽  
Response Curve ◽  
Calcium Ionophore ◽  
Receptor Activation ◽  
Inhibitory Effect ◽  
Rat Aorta ◽  
Calcium Ionophore A23187 ◽  
Ionophore A23187 ◽  
Acetylcholine Concentration ◽  
Concentration Response Curve

Background Previous study has shown that fentanyl attenuates acetylcholine-induced vasorelaxation. The goal of the current in vitro study was to identify the muscarinic receptor subtype that is mainly involved in the fentanyl-induced attenuation of endothelium-dependent relaxation elicited by acetylcholine. Methods The effects of fentanyl and muscarinic receptor antagonists on the acetylcholine concentration-response curve were assessed in aortic vascular smooth muscle ring preparations precontracted with phenylephrine. In the rings pretreated independently with pirenzepine, 4-diphenylacetoxyl-N-methylpiperidine methiodide, and naloxone, acetylcholine concentration-response curves were generated in the presence and absence of fentanyl. The effect of fentanyl on the concentration-response curve for calcium ionophore A23187 was assessed. Results Fentanyl (0.297 x 10 0.785 x 10 m) attenuated acetylcholine-induced vasorelaxation in ring preparations with or without 10 m naloxone. Pirenzepine (10 to 10 m) and 4-diphenylacetoxyl-N-methylpiperidine methiodide (10 to 10 m) produced a parallel rightward shift in the acetylcholine concentration-response curve. The concentrations (-log M) of pirenzepine and 4-diphenylacetoxyl-N-methylpiperidine methiodide necessary to displace the concentration-response curve of an acetylcholine by twofold were estimated to be 6.886 +/- 0.070 and 9.256 +/- 0.087, respectively. Methoctramine, 10 m, did not alter the acetylcholine concentration-response curve. Fentanyl, 0.785 x 10 m, attenuated acetylcholine-induced vasorelaxation in the rings pretreated with 10 m pirenzepine but had no effect on vasorelaxation in the rings pretreated with 10 m 4-diphenylacetoxyl-N-methylpiperidine methiodide. Fentanyl, 0.785 x 10 m, did not significantly alter calcium ionophore A23187-induced vasorelaxation. Conclusions These results indicate that fentanyl attenuates acetylcholine-induced vasorelaxation via an inhibitory effect at a level proximal to nitric oxide synthase activation on the pathway involving endothelial M3 muscarinic receptor activation in rat aorta.

scholarly journals Phosphorylase a activity as an indicator of neutrophil activation by chemotactic peptide.

1985 ◽  
Vol 101 (4) ◽  
pp. 1191-1197 ◽  
Author(s):  
J L Slonczewski ◽  
M W Wilde ◽  
S H Zigmond
Keyword(s):  
Glycogen Phosphorylase ◽  
Calcium Ionophore ◽  
Fold Increase ◽  
Dose Dependence ◽  
Calcium Ionophore A23187 ◽  
Ionophore A23187 ◽  
Cytoplasmic Calcium ◽  
Chemotactic Peptide ◽  
Transient Activation ◽  
Fold Activation

The activity of glycogen phosphorylase, an enzyme that is activated by both cAMP and calcium, was used as an indicator of the state of the cytoplasm after chemotactic stimulation of polymorphonuclear leukocytes (neutrophils). The activity of the enzyme showed a clear dependence on cytoplasmic calcium. Addition of the calcium ionophore A23187 caused a 4-5-fold increase in activity of phosphorylase a. In the absence of external Ca2+, A23187 caused only brief transient activation of phosphorylase; probably reflecting release of sequestered intracellular Ca2+. Addition of the chemotactic peptide N-formylnorleucylleucylphenylalanine (FNLLP) caused a transient 2-3-fold activation of the enzyme. The dose-dependence of activation by FNLLP showed a peak at 10(-8) M, near the Kd of the receptor for FNLLP. The phosphorylase activity peaks by 90 s and then declines, returning to basal levels by 20 min after stimulation with 10(-8) M peptide and by 60 min with 10(-7) M peptide. This finding suggests that the cells do not need to maintain elevated cytoplasmic calcium levels to exhibit stimulated locomotion. Thus, if calcium continues to modulate the motility, there either must be highly localized changes that are not detected in measures of the total cytoplasm, or the sensitivity to calcium must be variable such that basal levels are sufficient to maintain locomotion. Cells loaded with the fluorescence calcium probe quin2 (0.6 mM) in the presence or absence of external Ca2+ had elevated phosphorylase levels before addition of FNLLP. Thus, the presence of quin2 may alter the cytoplasmic Ca2+ level, and it clearly alters some aspects of the neutrophil physiology. Phosphorylase a appears to be a sensitive, nonperturbing indicator of the cytoplasmic calcium levels.

scholarly journals Binding of monoclonal antibody AA4 to gangliosides on rat basophilic leukemia cells produces changes similar to those seen with Fc epsilon receptor activation.

1992 ◽  
Vol 116 (3) ◽  
pp. 635-646 ◽  
Author(s):  
C Oliver ◽  
N Sahara ◽  
S Kitani ◽  
A R Robbins ◽  
L M Mertz ◽  
...  
Keyword(s):  
Histamine Release ◽  
Calcium Ionophore ◽  
Receptor Activation ◽  
Calcium Ionophore A23187 ◽  
Rat Tissues ◽  
Ionophore A23187 ◽  
Ige Receptor ◽  
Culture Dish ◽  
Basophilic Leukemia

The mAb AA4 binds to novel derivatives of the ganglioside Gd1b on rat basophilic leukemia (RBL-2H3) cells. Some of the gangliosides are located close to the high affinity IgE receptor (Fc epsilon RI), and binding of mAb AA4 inhibits Fc epsilon RI-mediated histamine release. In the present study, mAb AA4 was found to bind exclusively to mast cells in all rat tissues examined. In vitro, within 1 min of mAb AA4 binding, the cells underwent striking morphologic changes. They lost their normal spindle shaped appearance, increased their ruffling, and spread over the surface of the culture dish. These changes were accompanied by a redistribution of the cytoskeletal elements, actin, tubulin, and vimentin, but only the actin was associated with the membrane ruffles. Binding of mAb AA4 also induces a rise in intracellular calcium, stimulates phosphatidyl inositol breakdown, and activates PKC. However, the extent of these changes was less than that observed when the cells were stimulated with antigen or antibody directed against the Fc epsilon RI. None of these changes associated with mAb AA4 binding were seen when the cells were exposed to nonspecific IgG, IgE, or four other anti-cell surface antibodies, nor were the changes induced by binding mAb AA4 at 4 degrees C or in the absence of extracellular calcium. Although mAb AA4 does not stimulate histamine release, it enhances the effect of the calcium ionophore A23187 mediated release. The morphological and biochemical effects produced by mAb AA4 are similar to those seen following activation of the cell through the IgE receptor. Therefore, the surface gangliosides which bind mAb AA4 may function in modulating secretory events.

Inhibitory modulation by cAMP of isoproterenol-induced prostacyclin synthesis in rabbit heart

1989 ◽  
Vol 257 (4) ◽  
pp. R771-R780
Author(s):  
J. L. Williams ◽  
K. U. Malik
Keyword(s):  
Adrenergic Receptor ◽  
Calcium Ionophore ◽  
Phosphodiesterase Inhibitors ◽  
Rabbit Heart ◽  
Receptor Activation ◽  
Calcium Ionophore A23187 ◽  
Ionophore A23187 ◽  
Beta Adrenergic Receptor ◽  
Beta Adrenergic ◽  
Enhanced Production

beta-Adrenergic receptor activation in heart is associated with enhanced production of adenosine 3',5'-cyclic monophosphate (cAMP) and prostaglandins (PG). The purpose of the present study was to test the hypothesis that cAMP mediates or modulates PG synthesis elicited by activation of beta-adrenergic receptors in the isolated, perfused rabbit heart. Infusion of 8-(4-chlorophenylthio) (cpt)-cAMP (100 microM), an analogue of cAMP, or stimulation of endogenous cAMP generation with forskolin (2 microM) resulted in a reduction of perfusion pressure and an increase in heart rate and contractility but had no effect on 6-keto-PGF1 alpha output. 6-Keto-PGF1 alpha production elicited by a bolus injection of isoproterenol (Isop) (475 pmol), however, was reduced by greater than 50% in the presence of these agents, cpt-cAMP was also found to inhibit 6-keto-PGF1 alpha output elicited by the calcium ionophore A23187 but not that in response to exogenous arachidonic acid. Perfusion with the adenosine analogue adenylate cyclase inhibitor PIA (1 microM) enhanced by twofold Isop-stimulated output of 6-keto-PGF1 alpha, whereas cAMP accumulation was prevented. Isop-stimulated production of 6-keto-PGF1 alpha was inhibited by 50% in the presence of the phosphodiesterase inhibitors 1-methyl-3-isobutylxanthine (50 microM), Ro 20-1724 (300 microM), or cilostamide (5 microM), whereas both basal and Isop-stimulated cAMP accumulations were enhanced by these agents. These data suggest that cAMP acts as an inhibitory modulator of PG synthesis in response to beta-adrenergic receptor activation in rabbit heart.

Role of calcium and cAMP in the regulation of rat submandibular mucin secretion

1981 ◽  
Vol 241 (1) ◽  
pp. C76-C85 ◽  
Author(s):  
D. O. Quissell ◽  
K. A. Barzen ◽  
J. L. Lafferty
Keyword(s):  
Adrenergic Receptor ◽  
Calcium Ionophore ◽  
Receptor Activation ◽  
Calcium Ionophore A23187 ◽  
Secretory Response ◽  
Ionophore A23187 ◽  
Adrenergic Stimulation ◽  
Mucin Secretion ◽  
Mucin Release

The role of cellular adenosine 3',5'-cyclic monophosphate (cAMP) and calcium in the secretion of [14C]glucosamine-labeled mucins by rat submandibular acinar cells was studied. cAMP appeared to be involved, since 1-methyl-3-isobutylxanthine potentiated the secretory response and cellular cAMP levels increased dramatically following adrenergic stimulation. Furthermore, cAMP analogues were able to elicit a secretory response in the absence of beta-adrenergic receptor activation. Cellular calcium was required for mucin secretion at the level of cAMP action; depletion of cellular calcium by pretreatment with EGTA inhibited the secretory response to both adrenergic stimulation and exogenous cAMP addition, but pretreatment with EGTA did not alter the rise in cellular cAMP induced by norepinephrine. Extracellular calcium was not required to elicit mucin secretion, nor could secretion be elicited by means of the calcium ionophore A23187 alone. However, extracellular calcium may have an important biological role in mucin secretion, since cholinergic receptor activation and alpha-adrenergic receptor activation in conjunction with beta-adrenergic receptor activation potentiated mucin release. In addition, the calcium ionophore A23187 potentiated mucin release following cAMP analogue addition.

scholarly journals Changes in cytoplasmic calcium determine the secretory response to extracellular cations in human parathyroid cells: a confocal microscopy study using FM1-43 dye

2000 ◽  
Vol 352 (2) ◽  
pp. 353-361 ◽  
Author(s):  
Radu MIHAI ◽  
Teresa LAI ◽  
George J. SCHOFIELD ◽  
John R. FARNDON
Keyword(s):  
Confocal Microscopy ◽  
Plasma Membranes ◽  
Calcium Concentration ◽  
Membrane Surface ◽  
Calcium Ionophore ◽  
Calcium Ionophore A23187 ◽  
Ionophore A23187 ◽  
Cytoplasmic Calcium ◽  
Acetoxymethyl Ester ◽  
Prolonged Incubation

Whether activation of the calcium receptor (CaR) modulates secretory events was investigated by real-time fluorescence and confocal microscopy using fura 2 and FM1-43 fluorescent dye. Two paradigms were used: human parathyroid cells, which are stimulated by a step from a high to a low extracellular calcium concentration ([Ca2+]ext), and rMTC6-23 cells, a rat medullary thyroid carcinoma cell line whose secretion is stimulated by an increase in [Ca2+]ext. Parathyroid cells were dispersed from parathyroid adenomas removed from 18 patients with primary hyperparathyroidism. In both cell types, incubation with FM1-43 (2µM) resulted in staining of the plasma membranes, which was rapidly increased following changes in [Ca2+]ext known to stimulate secretion. A high [Ca2+]ext and lanthanum (La3+) decreased the membrane-associated FM1-43 fluorescence. Prolonged incubation (5–30min) in the presence of FM1-43 resulted in accumulation of the dye in the cytoplasm, its granular distribution suggesting targeting of the secretory compartment. These data suggest that FM1-43 fluorescence is determined by: (i) changes in cell membrane surface area associated with secretion-associated events, (ii) displacement/quenching by extracellular cations and (iii) endocytosis of the dye. In parathyroid cells, a rise in FM1-43 fluorescence occurred during incubation in a high (inhibitory) [Ca2+]ext if the cytoplasmic calcium concentration ([Ca2+]i) was decreased by the calcium chelator BAPTA/AM [bis-(o-aminophenoxy)ethane-N,N,Nƀ,Nƀ-tetra-acetic acid tetrakis(acetoxymethyl ester)] (10–50µM). Alternatively, the expected rise in FM1-43 fluorescence did not occur during incubation in a low (stimulatory) [Ca2+]ext if [Ca2+]i was increased by addition of the calcium ionophore A23187 (10–25µM). These data suggest that [Ca2+]i, rather than the absolute value of [Ca2+]ext, is the main modulator of secretion from parathyroid cells.

scholarly journals Regulation of synthesis of guanosine 3′:5′-cyclic monophosphate in neuroblastoma cells

1978 ◽  
Vol 176 (1) ◽  
pp. 119-127 ◽  
Author(s):  
T Bartfai ◽  
X O Breakefield ◽  
P Greengard
Keyword(s):  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Neuroblastoma Cells ◽  
Calcium Ionophore ◽  
Competitive Inhibitor ◽  
Receptor Activation ◽  
Calcium Ionophore A23187 ◽  
Soluble Form ◽  
Ionophore A23187 ◽  
Regulation Of Synthesis

The increase in intracellular cyclic GMP concentrations in response to muscarinic-receptor activation in N1E-115 neuroblastoma cells is dependent on extracellular Ca2+ ion. The calcium ionophore A23187 can also evoke an increase in cyclic GMP in the presence of Ca2+ ion. Most (about 85%) of the guanylate cyclase activity of broken-cell preparations is found in the soluble fraction. The soluble enzyme can utilize MnGTP (Km = 55 micrometer), MgGTP (Km = 310 micrometer) and CaGTP (Km greater than 500 micrometer) as substrates. Free GTP is a strong competitive inhibitor (Ki approximately 20 micrometer). The enzyme possesses an allosteric binding site for free metal ions (Ca2+, Mg2+ and Mn2+). The membrane-bound guanylate cyclase is qualitatively similar to the soluble form, but has lower affinity for the metal-GTP substrates. Entry of Ca2+ into cells may increase cyclic GMP concentration by activating guanylate cyclase through an indirect mechanism.

Growth factors and the primary cilium in BALB/c 3T3 cells

1987 ◽  
Vol 45 ◽  
pp. 830-831
Author(s):  
R. W. Tucker ◽  
N. S. More ◽  
S. Jayaraman
Keyword(s):  
Growth Factors ◽  
Primary Cilium ◽  
Cultured Cells ◽  
Morphological Changes ◽  
Calcium Ionophore ◽  
Growth Stimulation ◽  
Calcium Ionophore A23187 ◽  
Ionophore A23187 ◽  
3T3 Cells ◽  
Microtubule Depolymerization

The mechanisms by which polypeptide growth factors Induce DNA synthesis in cultured cells is not understood, but morphological changes Induced by growth factors have been used as clues to Intracellular messengers responsible for growth stimulation. One such morphological change has been the transient disappearance of the primary cilium, a “9 + 0” cilium formed by the perinuclear centriole in interphase cells. Since calcium ionophore A23187 also produced both mitogenesis and ciliary changes, microtubule depolymerization might explain ciliary disappearance monitored by indirect immunofluorescence with anti-tubulin antibody. However, complete resorption and subsequent reformation of the primary cilium occurs at mitosis, and might also account for ciliary disappearance induced by growth factors. To settle this issue, we investigated the ultrastructure of the primary cilium using serial thin-section electron microscopy of quiescent BALB/c 3T3 cells before and after stimulation with serum.

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