The effects of light on cyclic nucleotide metabolism of isolated cone photoreceptors.
A procedure has been developed for the isolation of cone photoreceptors from the retina of the lizard Anolis carolinensis in order to study the effects of dark- and light-adaptation on the cyclic nucleotide metabolism of these visual cells. Incubation of the retina in N2 medium with hyaluronidase and DNAase allows us to obtain intact photoreceptors with good purity (85-90%), yields (greater than 2 x 10(5) cells per retina), and more than 95% of them excluding Trypan blue. cAMP levels are 20-fold higher than cGMP levels in cells from dark-adapted animals and are decreased by 35% upon exposure to light, whereas cGMP levels show no apparent change. However, both cAMP- and cGMP-phosphodiesterases, as well as adenylate and guanylate cyclase, are activated several-fold by light, but the enzymes involved in cGMP metabolism have higher Vmaxs than the cAMP related enzymes. The apparent constant levels of cGMP found in cone photoreceptors may result from our inability to detect the very fast changes that occur in these cells when they are exposed to light.
Jules Stein Eye Institute, UCLA School of Medicine 90024-7008.
T L
TL
Denton
C K
CK
Yamashita
D B
DB
Farber
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism; D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000378:metabolism; D000221:Adaptation, Ocular / Q000502:physiology*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D003623:Dark Adaptation / Q000502:physiology; D006162:Guanylate Cyclase / Q000378:metabolism; D007700:Kinetics; D008027:Light; D008116:Lizards; D010786:Photoreceptor Cells / Q000201:enzymology / Q000378:metabolism*
D000242:Cyclic AMP; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase; D006152:Cyclic GMP