scholarly journals Specific binding sites for 5-hydroxytryptamine on rat blood platelets

1975 ◽  
Vol 150 (1) ◽  
pp. 129-132 ◽  
Author(s):  
A H Drummond ◽  
J L Gordon
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Blood Platelets ◽  
Rat Blood ◽  
Active Uptake ◽  
Specific Binding Sites

5-Hydroxytryptamine changes the shape of rat blood platelets by combination with a cinanserin-sensitive receptor which is not associated with the active uptake of 5-hydroxytryptamine. Binding of 5-hydroxy[3H]tryptamine to platelets at 4°C demonstrates the presence of three saturable sites, and the highest-affinity site is apparently this 5-hydroxytryptamine receptor.

Specific binding sites for 5-hydroxytryptamine on rat blood platelets

1975 ◽  
Vol 152 (3) ◽  
pp. 433.b1-433.b1
Author(s):  
A H Drummond ◽  
J L Gordon
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Blood Platelets ◽  
Rat Blood ◽  
Specific Binding Sites

Receptors for 5-Hydroxytryptamine on Rat Blood Platelets

1975 ◽  
Author(s):  
A. H. Drummond ◽  
J. L. Gordon
Keyword(s):  
Binding Sites ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Blood Platelets ◽  
Close Correlation ◽  
Inhibitory Potency ◽  
Rat Blood ◽  
Active Uptake ◽  
Platelet Shape ◽  
Rat Platelets

When 5-hydroxytryptamine (5HT) or its analogue, 5-methoxy-α-methyltryptamine (5MOαMT) are added to rat citrated platelet-rich plasma (PRP), the platelets change in shape but do not aggregate. The response to both of these agents is inhibited by the 5HT antagonist, cinanserin (IC50 = 3 व 10-9 M). Cinanserin is at least 10,000 times less potent against the active uptake of 5HT (IC50 > 5 व 10-5 M). 5MOαMT is not actively transported by the platelet, although some instantaneous binding can be measured which is independent of temperature (4°-37°). 5MOαMT does not inhibit 5HT uptake over the concentration range at which it induces the shape change (10-8-10-5 M). Binding of (3H)-5HT to rat platelets at 4° indicates the presence of three binding sites, one of which is specifically blocked by cinanserin (IC50 = 2.8 × l0-9 M). Close correlation between the inhibitory potency of various drugs against (3H)-5HT binding and 5HT-induced shape change suggests that this site is the 5HT receptor on the platelet which initiates the shape change. Our results indicate that 5HT induces the platelet shape change by combination with a specific cinanserinsensitive 5HT receptor, which is unconnected with the uptake site.

scholarly journals Specific Binding of Rubidium in Chlorella

1962 ◽  
Vol 45 (5) ◽  
pp. 959-977 ◽  
Author(s):  
Dan Cohen
Keyword(s):  
Active Transport ◽  
Binding Sites ◽  
Specific Binding ◽  
High Concentration ◽  
External Concentration ◽  
Specific Binding Sites ◽  
Dense Suspension ◽  
Concentration Of Ions ◽  
The Individual ◽  
A Site

Specific binding sites for potassium, which may be components of the carriers for active transport for K in Chlorella, were characterized by their capacity to bind rubidium. A dense suspension was allowed to take up Rb86 from a low concentration of Rb86 and a high concentration of ions which saturate non-specific sites. The amount bound was derived from the increase in the external concentration of Rb86 following addition of excess potassium. The sites were heterogeneous. The average affinity of Rb and various other ions for the sites was determined by plotting the degree of displacement of Rb86 against log molar concentration of the individual ions. Interpolation gave the concentration for 50 per cent displacement of Rb, which is inversely related to affinity. The order of affinity was not changed when the cells were frozen, or boiled either in water or in 70 per cent ethanol. The affinity is maximal for ions with a crystalline radius of 1.3 to 1.5 A and a high polarizability, and is not related to the hydrated radius or valency. It is suggested that binding groups in a site are rigidly arranged, the irregular space between them being 2.6 to 3.0 A across, so that affinity is high for ions of this diameter and high polarizability.

Studies of the uptake of macromolecules by cells. I. Uptake of proteins by cells of the Ehrlich–Lettré ascites carcinoma

1968 ◽  
Vol 46 (12) ◽  
pp. 1443-1450 ◽  
Author(s):  
Y. C. Choi ◽  
E. R. M. Kay
Keyword(s):  
Nucleic Acid ◽  
Cell Membrane ◽  
Binding Sites ◽  
Specific Binding ◽  
Protein Uptake ◽  
Specific Binding Sites ◽  
Model Protein ◽  
Uptake Process ◽  
Kinetics Of ◽  
Protein Treatment

The uptake of protein by cells of the Ehrlich–Lettré ascites carcinoma was characterized kinetically by using hemoglobin as a model protein. An attempt was made to show that the process is not an artefact due to nonspecific adsorption of protein to the cell membrane. The kinetics of the uptake process suggested that an interaction exists between the exogenous protein and specific binding sites on the membrane. Acetylation of hemoglobin enhanced the rate of uptake of this protein. Treatment of cells with neuraminidase, phospholipase A, and Pronase resulted in an inhibition of protein uptake. The experimental evidence for the uptake of hemoglobin was supported by evidence that L-serine-U-14C-labelled hemoglobin is transported into the cytoplasm and utilized subsequently, resulting in labelling of the nucleic acid nucleotides.

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