Immunoreactive atrial natriuretic peptide in the retina of rats and rabbits

Immunoreactive atrial natriuretic peptide (ANP) has been detected in retinal tissue by radioimmunoassay, although it is unclear whether it was in retinal cells or represented residual peptide from blood and/or ocular fluids. We report here, using the immunoperoxidase method and a highly specific anti-rat ANP, that the peptide was localized consistently in the outer and inner plexiform layers of retinas of rats and rabbits. This information raises important issues: what are the implications for retinal function and, since blood-borne radioligands do not reveal retinal 'receptors', what is the endogenous target of retinal ANP?