Development of A1 adenosine receptors in the chick embryo retina

✍ Scribed by R. Paes de Carvalho

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 685 KB
• Volume: 25
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/jnr.490250212

✦ Synopsis

Adenosine inhibits cyclic AMP synthesis induced by dopamine in embryonic but not in post-hatched chick retinas. N6-Cyclohexyladenosine (CHA), which preferentially activates A, receptors as well as 2-chloroadenosine, inhibits cyclic AMP accumulation induced by dopamine in retinas from 10-day-old embryos (E10) with ICJo's of 0.1 and 0.5 pM, respectively, but this effect is not detectable after hatching. In order to verify if this developmental change reflects variations in the number or affinity of A, adenosine receptors, their development during chick retina ontogeny was studied. Binding studies using 3(H)CHA revealed the presence of A, receptors at all stages of development examined, including the post-hatched retina. The number of binding sites increased between El0 and E17, and then decreased in post-hatched animals. In the latter, 3(H)CHA binding was to a single site with a B, , , of 128.6 f 13.4 fmol/mg protein and a K, of 2.1 + 0.2 nM. Various ligands showed similar hierarchies of affinity for the A, receptor in embryonic and post-hatched retinas, namely, CHA> R-N6-phenylisopropyladenosine (l-PIA)> 5'-N-ethylcarboxamideadenosine (NECA)> isobuthylmethyl-xanthine (IBMX). Given that CHA inhibited forskolin-induced cyclic AMP production and Gpp(NH)p inhibited 3(H)CHA binding in both embryonic and posthatched retinas, it appears that receptor coupling to adenylate cyclase is present since early embryonic stages. The results suggest that the A, receptors may have different functions in the embryonic as compared to the mature chick retina.