Cyclic nucleotides and protein kinase systems in the developing chick retina and pigment epithelium

During embryonic development of the chick neural retina, cyclic nucleotide levels are relatively uniform but rise abruptly at the time of hatching. The rise is thus not temporally correlated with features of morphological development such as outer segment elongation but rather with the onset of actual visual function. In the pigment epithelium, the cyclic AMP level declines throughout the embryonic period studied and does not rise at hatching. Cyclic GMP levels are much lower in both retina and pigment epithelium but rise several-fold at hatching. A binding protein is observed for cyclic AMP in the retina prior to outer segment development; cyclic GMP binding is considerably lower. Retinal ATP-kinase activity is high throughout the embryonic period studied and is stimulated up to 6-fold by 1 muM cyclic AMP and by 100 muM cyclic GMP. The major rise in GTP-kinase activity correlates temporally with photoreceptor outer segment development and may be involved intimately in the visual process.