Retinal cyclic GMP and AMP in rod-cone dysplasia: comparison of assays in fixed and unfixed retinal tissues

The effects of 3 fixatives (formalin, Bouin's solution and glutaraldehyde-paraformaldehyde) on retinal cyclic AMP and GMP content were determined in canine eyes with a known abnormality of cyclic GMP metabolism. Cyclic nucleotides were measured by radioimmunoassay on perchloric acid (PCA)-precipitated retinal samples from fixed (left) and unfixed (right) eyes from nine 6-week-old rod-cone-dysplasia-affected Irish setter dogs. Cyclic AMP values were significantly lower for fixed retinas than for unfixed controls. Retinal cyclic GMP values were also lower from glutaraldehyde-paraformaldehyde-fixed samples, but were not different from control values for formalin- or Bouin's-fixed eyes, when the retina was PCA-precipitated promptly after fixation.