Purpose: To determine by immunohistochemistry the distribution of different nitric oxide synthases (NOS) isoforms in the porcine eye.
Methods: By light microscopy (immunofluorescence), porcine ocular tissues were investigated using monoclonal antibodies against neuronal NOS (nNOS; NOS I), endothelial NOS (ecNOS; NOS III), and macrophage NOS (macNOS; NOS II).
Results: Specific nNOS immunoreactivity was detected along the apical cytoplasmic portions of the non-pigmented and pigmented ciliary epithelial cells, in the endothelial lining of the corneoscleral meshwork and the uveal cords of the iridocorneal angle tissue, as well as in the photoreceptor layer of the sensory retina. Immunoreactivity for ecNOS was confined to the vascular endothelium of the vessels of the conjunctiva, iris, ciliary body, retina, choroid and optic nerve. A mild immunostaining for macNOS was present in the cytoplasm of some non-pigmented ciliary epithelial cells.
Conclusions: The predominant localization of nNOS in ciliary epithelial and trabecular endothelial cells suggests a possible involvement of nNOS in both the production and outflow of aqueous humor in porcine eyes.