Bovine Brain Coated Vesicles Contain Adenosine A1 Receptors. Presence of Adenylate Cyclase Coupled to the Receptor

Abstract:

Clathrin‐coated vesicles purified from bovine brain express adenosine A1 receptor binding activity. N6‐Cyclohexyl[3H]adenosine ([3H]CHA), an agonist for the A1 receptor, binds specifically to coated vesicles. High and low agonist affinity states of the receptor for the radioligand [3H]CHA with KD values of 0.18 and 4.4 nM, respectively, were detected. The high purity of coated vesicles was established by assays for biochemical markers and by electron microscopy. Binding competition experiments using agonists N6CHA, N‐cyclopentyladenosine, 5′‐(N‐ethylcarboxamido)adenosine, and N6‐[(R)‐ and N6‐[(S)‐phenylisopropyl]adenosine and antagonists (theophylline, 3‐isobutyl‐1‐methylxanthine, and caffeine) confirmed the typical adenosine A1 nature of the binding site. This binding site presents stereospecificity for N6‐phenylisopropyladenosine, showing 33 times more affinity for N6‐[(R)‐ than for N6‐[(S …

Año de publicación:

1990

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Fuente:

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