Adenosine‐Elicited Accumulation of Adenosine 3′, 5′‐Cyclic Monophosphate in the Chick Embryo Retina

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Abstract
The cyclic AMP level of 17-day-old chick embryo retina increased from 20 to 331 pmol/mg protein when the tissue was incubated for 20 min in the presence of 4-(3-butoxy-4-methoxybenzyl-2-imidozolinone) (RO 20-1724). The addition of 0.5 mm-3-isobutyl-1-methylxanthine (IBMX) or 0.5 units/ml of adenosine deaminase (EC 3.5.4.4) to the medium reduced the increase of cyclic AMP content from 20 to 100 pmol/mg protein. Dipyridamole did not interfere with the rise of the retina cyclic AMP level observed with RO 20-1724. The EC50 of 6-amino-2-chloropurine riboside (2-chloroadenosine)-elicited accumulation of cylic AMP of retinas incubated in the presence of RO 20-1724 plus adenosine deaminase was approximately 1 μm. When retina incubation was carried out in the presence of 0.5 mm-IBMX, the 2-chloroadenosine dose–response curve was shifted to the right two orders of magnitude. Maximal stimulation of the cyclic AMP level of 17-day-old chick embryo retina incubated in the presence of 0.5 mm-IBMX was observed at 1 mm-adenosine concentration. This effect was not blocked by dopamine antagonists. Guanosine and adenine did not affect the retinal cyclic AMP level. AMP and ATP had a slight stimulatory effect. Adenosine response of embryonic retina increased sharply from the 14th to the 17th embryonic day. A similar, but not identical, adenosine effect was observed in cultured retina cells.