ISSN:
1573-4919
Keywords:
capillary endothelial cells
;
β-adrenoreceptor
;
cell proliferation
;
endothelial cell culture
;
angiogenesis
;
adenylate cyclase-cAMP system
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Abstract β-Adrenoreceptor has been studied in a clonal capillary endothelial cell line established from the vascular bed of the bovine adrenal medulla. [3H]Dihydroalprenolol ([3H]DHA) binding to the isolated plasma membranes from these cells has demonstrated the presence of β-adrenoreceptors with two different affinities. the dissociation constants (Kd) have been found to be 0.27±0.09×10−9 M and 2.96±0.31×10−9 M, respectively with the corresponding Bmax of 5.1±0.05 and 70.0±0.2 pmol/mg protein, respectively. Inhibition of [3H]DHA binding to the β-receptor by atenolol (a β1-antagonist) and ICI 118,551 (a β1-antagonist) has suggested that the IC50cor (=Ki) for atenolol and ICI 118,551 for high affinity site are 0.08±0.03×10−12 M and 0.25±0.08×10−12 M, respectively. This, therefore, indicates that both atenolol and ICI 118,551 are able to displace the bound ligand effectively but the β1-selective antagonist atenolol is 3 times more potent than its β2 counterpart, ICI 118,551. Displacement of [3H]DHA binding to the endothelial cell plasma membrane by the agonists isoproterenol, epinephrine and norephinephrine has established a relative order of Ki for these agents as isoproterenol (0.56±0.19×10−9 M)〈epinephrine (0.77±0.26−9 M)〉-norepinephrine (0.71±0.24×10−9 M) for the high affinity site. The corresponding values for the low affinity site, however, are 4.62±0.64×10−9 M, 6.21±0.86×10−9 M and 5.90±0.82×10−9 M, respectively for the same agonists. Increased intracellular cAMP accompanied with cellular proliferation in the presence of isoproterenol has suggested not only the coupling of β-adrenoreceptors to the adenylate cyclase system but also its involvement in endothelial cell proliferation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00928365
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