Immunohistochemical localization of cyclic GMP in goldfish retina.

The immunocytochemical procedure for cyclic GMP (cGMP) localization has been modified by the development of: 1) an anti-cGMP antibody depleted control serum and 2) a tissue preadsorption procedure that greatly reduces nonspecific fluorescence. cGMP remaining associated with tissue sections following prolonged exposure to aqueous buffer was determined, by extraction and measurement by radioimmunoassay, to be approximately 38% of the initial cGMP content. Application of this improved immunohistochemical procedure to goldfish retinas reveals the highest concentrations of cGMP to be associated with the cone inner segments and nuclei of the photoreceptors. This retinal distribution of cGMP is in good agreement with that independently determined by microdissection studies. The validity of this procedure is therefore strengthened and cautions to its application and interpretation are outlined.