This study provides a detailed description of immunolocalization of two oxygen-binding proteins, neuroglobin (Ngb) and cytoglobin (Cygb), in the anterior segment of healthy human and canine eyes. Specific antibodies against Ngb and Cygb were used to examine their distribution patterns in anterior segment structures including the cornea, iris, trabecular meshwork, canal of Schlemm, ciliary body, and lens. Patterns of immunoreactivity (IR) were imaged with confocal scanning laser and conventional microscopy. Analysis of sectioned human and canine eyes showed Ngb and Cygb IR in the corneal epithelium and endothelium. In the iris, Ngb and Cygb IR was localized to the anterior border and the stroma, iridal sphincter, and dilator muscle. In the iridocorneal angle, Ngb and Cygb were detected in endothelial cells of the trabecular meshwork and canal of Schlemm in human. In the ciliary body, Ngb and Cygb IR was localized to the non-pigmented ciliary epithelium of the pars plana and pars plicata and in ciliary body musculature. Ngb and Cygb distribution was similar and colocalized within the same structures of healthy human and canine anterior eye segments. Based on their immunolocalization and previously reported biochemical features, we hypothesize that Ngb and Cygb may function as scavengers of reactive oxygen species. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.
