Both endothelin-A and endothelin-B receptors are present on adult rat cardiac ventricular myocytes

2003 ◽  
Vol 81 (2) ◽  
pp. 95-104 ◽  
Author(s):  
Bruce G Allen ◽  
Luu Lien Phuong ◽  
Hala Farhat ◽  
Dominique Chevalier
Keyword(s):  
Incubation Temperature ◽  
Ventricular Myocytes ◽  
Cell Communication ◽  
Hill Coefficient ◽  
Receptor Subtype ◽  
Receptor Subtypes ◽  
Ligand Complex ◽  
Adult Rat ◽  
Endothelin A ◽  
Endothelin B

Endothelin-A (ETA) and endothelin-B (ETB) receptors have been demonstrated in intact heart and cardiac membranes. ETA receptors have been demonstrated on adult ventricular myocytes. The aim of the present study was to determine the presence of ETB and the relative contribution of this receptor subtype to total endothelin-1 (ET-1) binding on adult ventricular myocytes. Saturation binding experiments indicated that ET-1 bound to a single population of receptors (Kd = 0.52 ± 0.13 nM, n = 4) with an apparent maximum binding (Bmax) of 2.10 ± 0.25 sites (× 105)/cell (n = 4). Competition experiments using 40 pM [125I]ET-1 and nonradioactive ET-1 revealed a Ki of 660 ± 71 pM (n = 10) and a Hill coefficient (nH) of 0.99 ± 0.10 (n = 10). A selective ETA antagonist, BQ610, displaced 80% of the bound [125I]ET-1. No displacement was observed by concentrations of an ETB-selective antagonist, BQ788, up to 1.0 μM. However, in the presence of 1.0 μM BQ610, BQ788 inhibited the remaining [125I]ET-1 binding. Similarly, in the presence of 1.0 μM BQ788, BQ610 inhibited the remaining specific [125I]ET-1 binding. Binding of an ETB1-selective agonist, [125I]IRL-1620, confirmed the presence of ETB. ETB bound to ET-1 irreversibly, whereas binding to ETA demonstrated both reversible and irreversible components, and BQ610 and BQ788 bound reversibly. Reducing the incubation temperature to 0°C did not alter the irreversible component of ET-1 binding. Hence, both ETA and ETB receptors are present on intact adult rat ventricular myocytes, and the ratio of ETA:ETB binding sites is 4:1. Both receptor subtypes bind to ET-1 by a two-step association involving the formation of a tight receptor–ligand complex; however, the kinetics of ET-1 binding to ETA versus ETB differ.Key words: cell communication, endothelins, receptors, inotropic agents, signal transduction

Functional properties of Drosophila inositol trisphosphate receptors

2001 ◽  
Vol 359 (2) ◽  
pp. 435-441 ◽  
Author(s):  
Jane E. SWATTON ◽  
Stephen A. MORRIS ◽  
Frank WISSING ◽  
Colin W. TAYLOR
Keyword(s):  
Functional Properties ◽  
Inositol Trisphosphate ◽  
Stable State ◽  
Hill Coefficient ◽  
Receptor Subtype ◽  
Receptor Subtypes ◽  
S2 Cells ◽  
Ip3 Receptors ◽  
Ip3 Receptor ◽  
Adenophostin A

The functional properties of the only inositol trisphosphate (IP3) receptor subtype expressed in Drosophila were examined in permeabilized S2 cells. The IP3 receptors of S2 cells bound (1,4,5)IP3 with high affinity (Kd = 8.5±1.1nM), mediated positively co-operative Ca2+ release from a thapsigargin-sensitive Ca2+ store (EC50 = 75±4nM, Hill coefficient = 2.1±0.2), and they were recognized by an antiserum to a peptide conserved in all IP3 receptor subtypes in the same way as mammalian IP3 receptors. As with mammalian IP3 receptors, (2,4,5)IP3 (EC50 = 2.3±0.3μM) and (4,5)IP2 (EC50 approx. 10μM) were approx. 20- and 100-fold less potent than (1,4,5)IP3. Adenophostin A, which is typically approx. 10-fold more potent than IP3 at mammalian IP3 receptors, was 46-fold more potent than IP3 in S2 cells (EC50 = 1.67±0.07nM). Responses to submaximal concentrations of IP3 were quantal and IP3-evoked Ca2+ release was biphasically regulated by cytosolic Ca2+. Using rapid superfusion to examine the kinetics of IP3-evoked Ca2+ release from S2 cells, we established that IP3 (10μM) maximally activated Drosophila IP3 receptors within 400ms. The activity of the receptors then slowly decayed (t1/2 = 2.03±0.07s) to a stable state which had 47±1% of the activity of the maximally active state. We conclude that the single subtype of IP3 receptor expressed in Drosophila has similar functional properties to mammalian IP3 receptors and that analyses of IP3 receptor function in this genetically tractable organism are therefore likely to contribute to understanding the roles of mammalian IP3 receptors.

Distribution of α1-adrenoceptor subtype proteins in different tissues of neonatal and adult rats

2000 ◽  
Vol 78 (3) ◽  
pp. 237-243 ◽  
Author(s):  
Hao Shen ◽  
Krishna G Peri ◽  
Xing-Fei Deng ◽  
Sylvain Chemtob ◽  
Daya R Varma
Keyword(s):  
Vas Deferens ◽  
Polyclonal Antibodies ◽  
Receptor Subtype ◽  
Receptor Subtypes ◽  
Rat Tissues ◽  
Adult Rats ◽  
Adult Rat ◽  
Old Rats ◽  
Kidney Liver ◽  
The Brain

Distribution of α1-adrenoceptor (α1AR) subtype (α1A, α1B, α1D) proteins in brain, heart, kidney, and liver of 1-week-old rats and in brain, heart, aorta, kidney, liver, vas deferens, prostate, and adrenal glands of adult rats was investigated by Western analysis, using receptor subtype specific polyclonal antibodies. High levels of immunoreactive α1AAR and α1DAR in brain and heart and of α1BAR in liver and heart of neonatal rats were detected. In adult rat tissues, the abundance of α1AAR protein was most marked in the brain, intermediate in heart, aorta, liver, vas deferens, and adrenals, and minimal in the kidney and prostate; relative to other tissues, the expression of α1BAR was higher in brain and heart and that of α1DAR in brain. All the three receptor subtypes increased with age in the brain cortex, whereas the abundance of α1BAR increased in the heart but decreased in the liver; α1AAR and α1DAR in liver, kidney, and heart were not affected by age. It is concluded that α1AR subtypes are widely expressed in different neonatal and adult rat tissues.Key words: α1A-adrenoceptors, α1B-adrenoceptors, α1D-adrenoceptors, α1-adrenoceptor proteins.

scholarly journals β-Adrenergic Receptor Subtypes Differentially Affect Apoptosis in Adult Rat Ventricular Myocytes

Circulation ◽  
2000 ◽  
Vol 102 (3) ◽  
pp. 344-350 ◽  
Author(s):  
Michael Zaugg ◽  
Weimin Xu ◽  
Eliana Lucchinetti ◽  
Saiyid A. Shafiq ◽  
Nasir Z. Jamali ◽  
...  
Keyword(s):  
Adrenergic Receptor ◽  
Ventricular Myocytes ◽  
Receptor Subtypes ◽  
Rat Ventricular Myocytes ◽  
Adult Rat

Contractile regulation by overexpressed ETArequires intact T tubules in adult rat ventricular myocytes

2008 ◽  
Vol 294 (5) ◽  
pp. H2391-H2399 ◽  
Author(s):  
Ka Young Chung ◽  
Misuk Kang ◽  
Jeffery W. Walker
Keyword(s):  
Actin Polymerization ◽  
Ventricular Myocytes ◽  
Morphological Changes ◽  
Receptor Subtype ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Protein Levels ◽  
Intercalated Discs ◽  
T Tubules ◽  
G Protein Coupled

Endothelin (ET)-1 regulates the contractility and growth of the heart by binding G protein-coupled receptors of the ET type A receptor (ETA)/ET type B (ETB) receptor family. ETA, the predominant ET-1 receptor subtype in myocardium, is thought to localize preferentially within cardiac T tubules, but the consequences of mislocalization are not fully understood. Here we examined the effects of the overexpression of ETAin conjunction with T-tubule loss in cultured adult rat ventricular myocytes. In adult myocytes cultured for 3 to 4 days, the normally robust positive inotropic effect (PIE) of ET-1 was lost in parallel with T-tubule degeneration and a decline in ETAprotein levels. In these T tubule-compromised myocytes, an overexpression of ETAusing an adenoviral vector did not rescue the responsiveness to ET-1, despite the robust expression in the surface sarcolemma. The inclusion of the actin polymerization inhibitor cytochalasin D (CD) during culture prevented gross morphological changes including a loss of T tubules and a rounding of intercalated discs, but CD alone did not rescue the responsiveness to ET-1 or prevent ETAdownregulation. The rescue of a normal PIE in 3- to 4-day cultured myocytes required both an increased expression of ETAand intact T tubules (preserved with CD). Therefore, the activation of ETAlocalized in T tubules was associated with a strong PIE, whereas the activation of ETAin surface sarcolemma was not. The results provide insight into the pathological cardiac conditions in which ETAis upregulated and T-tubule morphology is altered.

scholarly journals GRKs as Modulators of Neurotransmitter Receptors

Cells ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 52
Author(s):  
Eugenia V. Gurevich ◽  
Vsevolod V. Gurevich
Keyword(s):  
G Protein ◽  
General Model ◽  
G Protein Coupled Receptors ◽  
Receptor Internalization ◽  
Neurotransmitter Receptors ◽  
Receptor Subtype ◽  
Receptor Subtypes ◽  
Receptor Kinase ◽  
G Protein Coupled ◽  
Homologous Desensitization

Many receptors for neurotransmitters, such as dopamine, norepinephrine, acetylcholine, and neuropeptides, belong to the superfamily of G protein-coupled receptors (GPCRs). A general model posits that GPCRs undergo two-step homologous desensitization: the active receptor is phosphorylated by kinases of the G protein-coupled receptor kinase (GRK) family, whereupon arrestin proteins specifically bind active phosphorylated receptors, shutting down G protein-mediated signaling, facilitating receptor internalization, and initiating distinct signaling pathways via arrestin-based scaffolding. Here, we review the mechanisms of GRK-dependent regulation of neurotransmitter receptors, focusing on the diverse modes of GRK-mediated phosphorylation of receptor subtypes. The immediate signaling consequences of GRK-mediated receptor phosphorylation, such as arrestin recruitment, desensitization, and internalization/resensitization, are equally diverse, depending not only on the receptor subtype but also on phosphorylation by GRKs of select receptor residues. We discuss the signaling outcome as well as the biological and behavioral consequences of the GRK-dependent phosphorylation of neurotransmitter receptors where known.

scholarly journals Transmitter and ion channel profiles of neurons in the primate abducens and trochlear nuclei

2021 ◽  
Author(s):  
Ümit Suat Mayadali ◽  
Jérome Fleuriet ◽  
Michael Mustari ◽  
Hans Straka ◽  
Anja Kerstin Ellen Horn
Keyword(s):  
Eye Movements ◽  
Ion Channel ◽  
Membrane Properties ◽  
Receptor Subtype ◽  
Receptor Subtypes ◽  
Voltage Gated ◽  
Calcium Ion Channels ◽  
Cell Type Specific ◽  
Transmitter Receptors ◽  
Intrinsic Membrane Properties

AbstractExtraocular motoneurons initiate dynamically different eye movements, including saccades, smooth pursuit and vestibulo-ocular reflexes. These motoneurons subdivide into two main types based on the structure of the neuro-muscular interface: motoneurons of singly-innervated (SIF), and motoneurons of multiply-innervated muscle fibers (MIF). SIF motoneurons are thought to provoke strong and brief/fast muscle contractions, whereas MIF motoneurons initiate prolonged, slow contractions. While relevant for adequate functionality, transmitter and ion channel profiles associated with the morpho-physiological differences between these motoneuron types, have not been elucidated so far. This prompted us to investigate the expression of voltage-gated potassium, sodium and calcium ion channels (Kv1.1, Kv3.1b, Nav1.6, Cav3.1–3.3, KCC2), the transmitter profiles of their presynaptic terminals (vGlut1 and 2, GlyT2 and GAD) and transmitter receptors (GluR2/3, NMDAR1, GlyR1α) using immunohistochemical analyses of abducens and trochlear motoneurons and of abducens internuclear neurons (INTs) in macaque monkeys. The main findings were: (1) MIF and SIF motoneurons express unique voltage-gated ion channel profiles, respectively, likely accounting for differences in intrinsic membrane properties. (2) Presynaptic glutamatergic synapses utilize vGlut2, but not vGlut1. (3) Trochlear motoneurons receive GABAergic inputs, abducens neurons receive both GABAergic and glycinergic inputs. (4) Synaptic densities differ between MIF and SIF motoneurons, with MIF motoneurons receiving fewer terminals. (5) Glutamatergic receptor subtypes differ between MIF and SIF motoneurons. While NMDAR1 is intensely expressed in INTs, MIF motoneurons lack this receptor subtype entirely. The obtained cell-type-specific transmitter and conductance profiles illuminate the structural substrates responsible for differential contributions of neurons in the abducens and trochlear nuclei to eye movements.

scholarly journals Effects of acidosis on resting cytosolic and mitochondrial Ca2+ in mammalian myocardium.

1993 ◽  
Vol 102 (3) ◽  
pp. 575-597 ◽  
Author(s):  
G Gambassi ◽  
R G Hansford ◽  
S J Sollott ◽  
B A Hogue ◽  
E G Lakatta ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Ventricular Myocytes ◽  
Free Acid ◽  
Left Ventricular ◽  
Ruthenium Red ◽  
Acetoxymethyl Ester ◽  
Cytosolic Ph ◽  
Bicarbonate Buffer ◽  
Adult Rat ◽  
Mammalian Myocardium

Acidosis increases resting cytosolic [Ca2+], (Cai) of myocardial preparations; however, neither the Ca2+ sources for the increase in Cai nor the effect of acidosis on mitochondrial free [Ca2+], (Cam) have been characterized. In this study cytosolic pH (pHi) was monitored in adult rat left ventricular myocytes loaded with the acetoxymethyl ester (AM form) of SNARF-1. A stable decrease in the pHi of 0.52 +/- 0.05 U (n = 16) was obtained by switching from a bicarbonate buffer equilibrated with 5% CO2 to a buffer equilibrated with 20% CO2. Electrical stimulation at either 0.5 or 1.5 Hz had no effect on pHi in 5% CO2, nor did it affect the magnitude of pHi decrease in response to hypercarbic acidosis. Cai was measured in myocytes loaded with indo-1/free acid and Cam was monitored in cells loaded with indo-1/AM after quenching cytosolic indo-1 fluorescence with MnCl2. In quiescent intact myocytes bathed in 1.5 mM [Ca2+], hypercarbia increased Cai from 130 +/- 5 to 221 +/- 13 nM. However, when acidosis was effected in electrically stimulated myocytes, diastolic Cai increased more than resting Cai in quiescent myocytes, and during pacing at 1.5 Hz diastolic Cai was higher (285 +/- 17 nM) than at 0.5 Hz (245 +/- 18 nM; P < 0.05). The magnitude of Cai increase in quiescent myocytes was not affected either by sarcoplasmic reticulum (SR) Ca2+ depletion with ryanodine or by SR Ca2+ depletion and concomitant superfusion with a Ca(2+)-free buffer. In unstimulated intact myocytes hypercarbia increased Cam from 95 +/- 12 to 147 +/- 19 nM and this response was not modified either by ryanodine and a Ca(2+)-free buffer or by 50 microM ruthenium red in order to block the mitochondrial uniporter. In mitochondrial suspensions loaded either with BCECF/AM or indo-1/AM, acidosis produced by lactic acid addition decreased both intra- and extramitochondrial pH and increased Cam. Studies of mitochondrial suspensions bathed in indo-1/free acid-containing solution showed an increase in extramitochondrial Ca2+ after the addition of lactic acid. Thus, in quiescent myocytes, cytoplasmic and intramitochondrial buffers, rather than transsarcolemmal Ca2+ influx or SR Ca2+ release, are the likely Ca2+ sources for the increase in Cai and Cam, respectively; additionally, Ca2+ efflux from the mitochondria may contribute to the raise in Cai. In contrast, in response to acidosis, diastolic Cai in electrically stimulated myocytes increases more than resting Cai in quiescent cells; this suggests that during pacing, net cell Ca2+ gain contributes to enhance diastolic Cai.

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