scholarly journals The Effects of Potassium Channel Openers and Blockers on the Specific Binding Sites for [3H]Glibenclamide in Rat Tissues

1995 ◽  
Vol 67 (1) ◽  
pp. 35-44 ◽  
Author(s):  
Toru Yamashita ◽  
Yukinori Masuda ◽  
Sakuya Tanaka
Keyword(s):  
Potassium Channel ◽  
Binding Sites ◽  
Specific Binding ◽  
Rat Tissues ◽  
Potassium Channel Openers ◽  
Specific Binding Sites

Atrial natriuretic factor binding sites in the jejunum

1989 ◽  
Vol 256 (2) ◽  
pp. G436-G441 ◽  
Author(s):  
C. Bianchi ◽  
G. Thibault ◽  
A. De Lean ◽  
J. Genest ◽  
M. Cantin
Keyword(s):  
Binding Sites ◽  
Atrial Natriuretic Factor ◽  
Specific Binding ◽  
Rat Tissues ◽  
Rat Jejunum ◽  
Specific Binding Sites ◽  
Natriuretic Factor ◽  
Atrial Natriuretic

We have studied the localization and the characterization of atrial natriuretic factor (ANF) binding sites by radioautographic techniques. Quantitative in vitro radioautography with a computerized microdensitometer demonstrated the presence of high-affinity, low-capacity 125I-ANF-(99-126) binding sites (Kd, 48 pM; Bmax, 63 fmol/mg protein) mainly in the villi of 20-microns slide-mounted transverse sections of the rat jejunum. Competition curves showed 50% inhibitory concentrations of 55 and 1,560 pM for ANF-(99-126) and ANF-(103-123), respectively. In vivo electron microscope radioautography showed that 80% of the silver grains were localized on the lamina propria fibroblast-like cells, 18% on mature enterocytes, and 2% on capillaries. Bradykinin and adrenocorticotropin did not compete with ANF binding. These results demonstrate that ANF binding sites in the rat jejunum possess the pharmacological characteristics of functional ANF receptors encountered in other rat tissues, and ultrastructural radioautographs show their cellular distribution. Taken together, these results demonstrate the presence and the localization of specific binding sites for ANF in the jejunal villi of the rat small intestine.

scholarly journals Direct in vivo demonstration by radioautography of specific binding sites for calcitonin in skeletal and renal tissues of the rat.

1980 ◽  
Vol 85 (3) ◽  
pp. 682-694 ◽  
Author(s):  
H Warshawsky ◽  
D Goltzman ◽  
M F Rouleau ◽  
J J Bergeron
Keyword(s):  
Binding Sites ◽  
Alveolar Bone ◽  
Specific Binding ◽  
Biologically Active ◽  
Target Cells ◽  
Rat Tissues ◽  
Specific Binding Sites ◽  
Calcitonin Receptors

An in vivo binding assay using radioautography was employed to visualize calcitonin receptors in rat tissues. At 2 min after intravenous injection of biologically active 125I-salmon calcitonin, free hormone was separated from bound hormone by intracardiac perfusion with lactated Ringer's followed by fixation with 2.5% glutaraldehyde. Various tissues were removed and processed for light and electron microscope radioautography. These were compared to tissues removed from animals that received identical amounts of labeled hormone with a large excess of unlabeled calcitonin. Among the tissues investigated, kidney and bone demonstrated labeling. In kidney, most silver grains were located over vesicles below the brush border of cells of theproximal convoluted tubules. These grains were still present after simultaneous injection of excess unlabeled hormone and most likely represented binding to sites involved with ingestion and degradation of hormone from the urinary filtrate. In contrast, grains localized to the basal surfaces of distal convoluted tubule cells were significantly reduced in number in control animals and represented sites of saturable, specific hormone binding. In bone, specific binding sites were found only at the periphery of osteoclasts. These labeled cells were located at resorption sites examined in tibia, humerus, and alveolar bone. This demonstration of the localization of 124I-calcitonin in situ provides a new approach for study the interaction of calcium-regulating hormones with their target cells.

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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