MATERIALS AND METHODS

Rats of the Fischer CDJ (control) or Royal College of Surgeons (RCS) strains were bred in a vivarium and reared under diurnal lighting conditions. These conditions were comparable to those used for studies of cyclic nucleotide metabolism in retinae of control and C3H (rd) mice. Animals were killed by decapitation at appropriate postnatal ages and, after enucleation, the light-adapted retinae were dissected with the aid of a microscope. Retinal homogenates were prepared in 50m~-Tris buffer (pH 7.6) containing 5 mM-MgCI, so as to yield approx 9Opg protein/30 pI. The protein content was determined by the method of LOWY et al.(1951). AC activity was determined in a final reaction mixture of 200 pI containing 50 mM-Tris (pH 7.6), 5 mM-MgCI,, 1 x lo-’M-ATP with about 1.5 x lo6 cpm of C3’P] ATP (specific activity 20 25 Ciimmol; New England Nuclear Corp.), 1 x lo-’M-cyclic AMP with 50,000 cpm of [3H] cyclic AMP (specific activity 37.7 Ci/mmol, New England Nuclear Corp.), 15 mM-phosphocreatine, 5.8 units of ATP: creatine phosphotransferase (Type I, rabbit muscle; Sigma), 10 mM-NaF, and 8 x lo-’M-isobutylmethylxanthine (Aldrich Chemical Co.). To evaluate the basal level 167