Relative effect of transmitter release depends only on transmitter baseline, not on maximum binding capacity

NeuroImage ◽  
2010 ◽  
Vol 52 ◽  
pp. S19
Author(s):  
Albert Gjedde ◽  
Jakob Linnet
Keyword(s):  
Transmitter Release ◽  
Binding Capacity ◽  
Relative Effect ◽  
Maximum Binding Capacity

Muscle Na+-K+-ATPase response during 16 h of heavy intermittent cycle exercise

2007 ◽  
Vol 293 (2) ◽  
pp. E523-E530 ◽  
Author(s):  
H. J. Green ◽  
T. A. Duhamel ◽  
G. P. Holloway ◽  
J. W. Moule ◽  
J. Ouyang ◽  
...  
Keyword(s):  
Aerobic Power ◽  
Intermittent Exercise ◽  
Binding Capacity ◽  
Vastus Lateralis ◽  
Intrinsic Activity ◽  
Cycle Exercise ◽  
Maximum Binding Capacity ◽  
Phosphatase Assay ◽  
Quantitative Immunoblotting

This study investigated the effects of a 16-h protocol of heavy intermittent exercise on the intrinsic activity and protein and isoform content of skeletal muscle Na+-K+-ATPase. The protocol consisted of 6 min of exercise performed once per hour at ∼91% peak aerobic power (V̇o2 peak) with tissue sampling from vastus lateralis before (B) and immediately after repetitions 1 (R1), 2 (R2), 9 (R9), and 16 (R16). Eleven untrained volunteers with a V̇o2 peak of 44.3 ± 2.3 ml·kg−1·min−1 participated in the study. Maximal Na+-K+-ATPase activity ( Vmax, in nmol·mg protein−1·h−1) as measured by the 3- O-methylfluorescein K+-stimulated phosphatase assay was reduced ( P < 0.05) by ∼15% with exercise regardless of the number of repetitions performed. In addition, Vmax at R9 and R16 was lower ( P < 0.05) than at R1 and R2. Vanadate-facilitated [3H]ouabain determination of Na+-K+-ATPase content (maximum binding capacity, pmol/g wet wt), although unaltered by exercise, increased ( P < 0.05) 8.3% by R9 with no further increase observed at R16. Assessment of relative changes in isoform abundance measured at B as determined by quantitative immunoblotting showed a 26% increase ( P < 0.05) in the α2-isoform by R2 and a 29% increase in α3 by R9. At R16, β3 was lower ( P < 0.05) than at R2 and R9. No changes were observed in α1, β1, or β2. It is concluded that repeated sessions of heavy exercise, although resulting in increases in the α2- and α3-isoforms and decreases in β3-isoform, also result in depression in maximal catalytic activity.

Specific binding of serotonin in rat lung

1985 ◽  
Vol 248 (1) ◽  
pp. E58-E63 ◽  
Author(s):  
D. K. Das ◽  
H. Steinberg
Keyword(s):  
Binding Capacity ◽  
Specific Binding ◽  
Direct Action ◽  
High Capacity ◽  
Mitochondrial Fraction ◽  
Temperature Sensitive ◽  
Inner Mitochondrial Membrane ◽  
High Affinity ◽  
Single Temperature ◽  
Maximum Binding Capacity

Mammalian lungs have been shown to store and to inactivate serotonin (5-HT) by an active process involving uptake and metabolism. 5-HT has direct action on lung including constrictor effects of pulmonary vascular and tracheobronchial smooth muscle, suggesting the presence of 5-HT receptors in lung. We have identified specific 5-HT binding of high affinity to the different lung portions and have shown that there was a different capacity for this binding. Two different 5-HT-binding capacities are present in a purified mitochondrial fraction. Saturation analysis of 5-[3H]HT binding to outer mitochondrial membranes demonstrates a single, temperature-sensitive, high-affinity and high-capacity binding (Kd = 8.3 +/- 1.2 nM, maximum binding capacity = 0.819 +/- 0.046 pmol/mg protein). The dissociation constant of inner mitochondrial membrane demonstrates a low-capacity site (Kd = 25.2 +/- 2.2 nM, maximum binding capacity = 0.453 +/- 0.037 pmol/mg protein). The purified microsomal fraction of lung exhibits a high-capacity binding site for 5-[3H]HT (Kd = 14.8 +/- 1.6 nM, maximum binding capacity = 0.760 +/- 0.03 pmol/mg protein). In addition to the lung being the major site for its inactivation, the presence of several specific 5-HT receptors may be related to some of the known 5-HT actions in lung and may suggest other unknown actions of this amine.

Distribution of opioid receptors in canine small intestine: implications for function

1989 ◽  
Vol 256 (6) ◽  
pp. G966-G974 ◽  
Author(s):  
H. D. Allescher ◽  
S. Ahmad ◽  
P. Kostka ◽  
C. Y. Kwan ◽  
E. E. Daniel
Keyword(s):  
Small Intestine ◽  
Binding Sites ◽  
Myenteric Plexus ◽  
Plasma Membranes ◽  
Binding Capacity ◽  
Opiate Receptors ◽  
Circular Muscle ◽  
Maximum Binding Capacity ◽  
Opiate Binding ◽  
Subtype Selective

Distribution of the binding sites for [3H]diprenorphine, a non-selective opiate ligand, was studied in membrane fractions from longitudinal muscle/myenteric plexus and circular muscle containing deep muscular plexus. [3H]saxitoxin was used as a marker for neuronal plasma membranes and 5'-nucleotidase as a marker for smooth muscle plasma membranes. Saxitoxin binding correlated strongly with diprenorphine binding, but 5'-nucleotidase correlated poorly with diprenorphine or saxitoxin binding in these fractions. Opiate binding sites in membranes of myenteric and deep muscular plexus were of high affinity (Kd = 0.12 and 0.18 nM, respectively) with maximum binding capacity of 400 and 500 fmol/mg protein, respectively. Competition experiments using subtype-selective opiate ligands indicated that all three subtypes of opiate receptors were present in the same ratio of 40-45% mu-subtypes, 40-45% delta-subtypes, and 10-15% kappa-subtypes on both plexuses. Opiate receptors of canine small intestine, therefore, are located primarily or exclusively on nerves with similar distributions in nerve membranes containing only axonal varicosities (deep muscular plexus) as in those containing neurons, dendrites, and varicosities (myenteric plexus).

ATP-MgCl2 treatment after trauma-hemorrhage/resuscitation increases hepatocyte P2-purinoceptor binding capacity

1994 ◽  
Vol 266 (6) ◽  
pp. R1810-R1815
Author(s):  
M. S. Mahmoud ◽  
P. Wang ◽  
S. R. Hootman ◽  
S. S. Reich ◽  
I. H. Chaudry
Keyword(s):  
Binding Capacity ◽  
Scatchard Analysis ◽  
Binding Characteristics ◽  
Beneficial Effects ◽  
High Affinity ◽  
Receptor Component ◽  
Receptor Dynamics ◽  
Maximum Binding Capacity ◽  
High Affinity Receptor ◽  
Affinity Receptor

Although our studies indicate that P2-purinoceptor binding capacity decreases after hemorrhage and resuscitation, it is not known whether ATP-MgCl2 administration after hemorrhage has any beneficial effects on the receptor dynamics. To study this, we performed laparotomy (i.e., trauma induced) on rats and bled them to and maintained them at a mean arterial pressure of 40 mmHg until 40% of maximum bleedout volume was returned in the form of Ringer lactate (RL). The animals were then resuscitated with 3 times the volume of maximum bleedout with RL over 45 min followed by 2 times RL along with ATP-MgCl2 (50 mumol/kg body wt) over 95 min. Hepatocytes were isolated at 4, 17, and 27 h after resuscitation. P2-purinoceptor binding characteristics were determined by using [alpha-35S]ATP. Scatchard analysis revealed high-affinity and low-affinity receptor components in the hepatocytes isolated from sham-operated or hemorrhaged animals with or without ATP-MgCl2 infusion. ATP-MgCl2 ameliorated and subsequently restored the decreased maximum binding capacity (Bmax) of the high-affinity receptor component and significantly improved Bmax of the low-affinity receptor component. ATP-MgCl2 administration also produced a progressive enhancement in the affinity of the low-affinity receptor component. Thus the beneficial effects of ATP-MgCl2 observed after trauma-hemorrhage and resuscitation may be, in part, due to the restoration of P2-purinoceptor binding capacity and the enhancement of the receptor affinity.

Isoproterenol Improves Secretion of Transplanted Submandibular Glands

2009 ◽  
Vol 88 (5) ◽  
pp. 477-482 ◽  
Author(s):  
Y.M. Li ◽  
Y. Zhang ◽  
L. Shi ◽  
B. Xiang ◽  
X. Cong ◽  
...  
Keyword(s):  
Submandibular Gland ◽  
Binding Capacity ◽  
Keratoconjunctivitis Sicca ◽  
Acinar Cells ◽  
Salivary Flow ◽  
Secretory Function ◽  
Receptor Signal ◽  
Maximum Binding Capacity ◽  
Wharton’S Duct ◽  
Structural Injury

Autotransplantation of the submandibular gland is effective for severe keratoconjunctivitis sicca. However, most transplants show decreased secretion shortly after the operation, which leads to obstruction of Wharton’s duct. The hypothesis that decreased catecholamine release due to denervation contributes to hypofunction in the early phase was tested in transplanted glands in rabbits. We found that salivary flow, expression of β1- and β2-adrenoceptor, and the maximum binding capacity were markedly decreased in the transplanted glands. Isoproterenol significantly reversed the decreased secretion, enhanced the expressions of β1- and β2-adrenoceptor, and ameliorated the atrophy of acinar cells. The contents of cAMP and phospho-ERK 1/2 were increased after isoproterenol treatment. These results indicate that lack of β-adrenoceptor stimulation is involved in early dysfunction of the transplanted gland. Isoproterenol treatment moderates structural injury and improves secretory function in the transplanted submandibular gland through up-regulating β1- and β2-adrenoceptor expression and post-receptor signal transduction.

scholarly journals Equilibrium binding of coenzymes and substrates to nicotinamide-adenine dinucleotide phosphate-linked isocitrate dehydrogenase from bovine heart mitochondria

1978 ◽  
Vol 171 (3) ◽  
pp. 733-742 ◽  
Author(s):  
C H Reynolds ◽  
P W Kuchel ◽  
K Dalziel
Keyword(s):  
Ionic Strength ◽  
Isocitrate Dehydrogenase ◽  
Binding Capacity ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Kinetic Properties ◽  
Protein Fluorescence ◽  
Fluorescence Measurements ◽  
Equilibrium Binding ◽  
Maximum Binding Capacity ◽  
Fluorescence Titrations

1. The stoicheiometries and affinities of ligand binding to isocitrate dehydrogenase were studied at pH 7.0, mainly by measuring changes in NADPH and protein fluorescence. 2. The affinity of the enzyme for NADPH is about 100-fold greater than it is for NADP+ in various buffer/salt solutions, and the affinities for both coenzymes are decreased by Mg2+, phosphate and increase in ionic strength. 3. The maximum binding capacity of the dimeric enzyme for NADPH, from coenzyme fluorescence and protein-fluorescence measurements, and also for NADP+, by ultrafiltration, is 2 mol/mol of enzyme. Protein-fluorescence titrations of the enzyme with NADP+ are apparently inconsistent with this conclusion, indicating that the increase in protein fluorescence caused by NADP+ binding is not proportional to fractional saturation of the binding sites. 4. Changes in protein fluorescence caused by changes in ionic strength and by the binding of substrates, Mg2+ or NADP+ (but not NADPH) are relatively slow, suggesting conformation changes. 5. In the presence of Mg2+, the enzyme binds isocitrate very strongly, and 2-oxoglutarate rather weakly. 6. Evidence is presented for the formation of an abortive complex of enzyme-Mg2+-isocitrate-NADPH in which isocitrate and NADPH are bound much more weakly than in their complexes with enzyme and Mg2+ alone. 7. The results are discussed in relation to the interpretation of the kinetic properties of the enzyme and its behaviour in the mitochondrion.

Uptake of 3,5,3′-l-tri-iodothyronine in human erythrocytes

1989 ◽  
Vol 121 (3) ◽  
pp. 585-591 ◽  
Author(s):  
K. Yamauchi ◽  
R. Horiuchi ◽  
H. Takikawa
Keyword(s):  
Binding Sites ◽  
Binding Capacity ◽  
Human Erythrocytes ◽  
The Other ◽  
Transport Pathway ◽  
High Affinity ◽  
High Affinity Site ◽  
Maximum Binding Capacity ◽  
Energy Dependent ◽  
Dependent Pathway

ABSTRACT The mechanisms of 3,5,3′-l-tri-iodothyronine (T3) uptake into human erythrocytes were examined. Purified membranes of human erythrocytes were shown to have two classes of T3-binding sites with one being a high-affinity site (dissociation constant, 59·2±17·8 nmol/l; maximum binding capacity, 344·3 ± 95·5 fmol/μg protein). Furthermore, it was shown that there were two pathways for T3 uptake in human erythrocytes; one was saturable, stereospecific (T3»thyroxine > 3,5,3′-d-tri-iodothyronine), energydependent and dominant at 15 °C; the other was not displaced by unlabelled T3 and was energyindependent but did not occur by passive diffusion. The former pathway which, it is suggested, is a receptor-mediated transport pathway, was inhibited by monodansylcadaverine, phloretin or oligomycin at 15 or 37 °C, but the latter pathway was not inhibited by these inhibitors. Our results strongly suggest that uptake of T3 by the energy-independent pathway became predominant over the energy-dependent pathway at 37 °C and accounted for 83% of total T3 uptake of human erythrocytes. Journal of Endocrinology (1989) 121, 585–591

scholarly journals Purification of the 22000- and 20000-mol.wt. forms of human somatotropin and characterization of their binding to liver and mammary binding sites

1983 ◽  
Vol 214 (3) ◽  
pp. 885-892 ◽  
Author(s):  
J Closset ◽  
J Smal ◽  
F Gomez ◽  
G Hennen
Keyword(s):  
Mammary Gland ◽  
Binding Capacity ◽  
Chemical Characterization ◽  
Rabbit Liver ◽  
Partial Agonists ◽  
Affinity Constants ◽  
Pregnant Rabbit ◽  
Maximum Binding Capacity ◽  
Specificity Of Binding

Quantitative data concerning the binding of 22000-mol.wt. human somatotropin and its 20000-mol.wt. variant are described using pregnant-rabbit liver and mammary-gland receptors. The purification and the complete chemical characterization of both human somatotropin and its 20000-mol.wt. variant is also presented. Contamination of the 20000-mol.wt.-variant preparation by 22000-mol.wt. hormone was found to be 0.5% by weight as measured in radioimmunoassay using monoclonal antibody. Labelling of human somatotropin and its 20000-mol.wt. variant using the Iodogen method is described as well as the characterization of the binding to pregnant-rabbit liver and mammary-gland receptor preparations. The maximum binding capacity of the 125I-labelled human somatotropin was between 50 and 60% to liver particulate receptor, whereas that of the 20000-mol.wt. variant was 30%. The specificity of binding of both forms to rabbit hepatic and mammary-gland receptor was found to be similar for both proteins in the same system. The affinity constants and capacity were respectively 0.7 X 10(10)M-1 and 815 fmol/mg of protein for human somatotropin and 0.6 X 10(10)M-1 and 1.250 fmol/mg of protein for the 20000-mol.wt. variant. These data suggest that both proteins behave as partial agonists to the receptors studied.

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