Neuroglobin and cytoglobin distribution patterns in human and canine eye
Globins are a family of heme-containing proteins that reversibly bind gaseous ligands such as oxygen, nitric oxide and carbon monoxide. Neuroglobin (Ngb) and cytoglobin (Cygb) have been recently added to mammalian globin family. The general hypothesis of this dissertation was: The presence of Ngb and Cygb can be detected by biochemical and immunohistochemical methods in different structures of the eye;Ngb immunoreactivity (IR) in the canine retina was located in the ganglion cell layer (GCL), inner (INL) and outer nuclear layers (ONL), inner (IPL) and outer plexiform layers (OPL), photoreceptor inner segments (IS) and retinal pigment epithelium (RPE). Cygb-IR in the canine retina was found in the GCL, INL and ONL, IPL and OPL and RPE. Ngb and Cygb were expressed in the same cells in the GCL and INL. Distribution pattern of Ngb and Cygb in human retina was similar to distribution found in the canine retina;Ngb and Cygb-IR in the human and canine anterior segment structures was detected in the corneal epithelium and endothelium. Furthermore, in the iris, Ngb and Cygb-IR was localized to the anterior border layer and the stroma, iridal sphincter and dilator muscle. In the iridocorneal angle, both Ngb and Cygb were detected in endothelial cells of the human and canine trabecular meshwork and canal of Schlemm in human. In the ciliary body, Ngb- and Cygb-IR was localized to the nonpigmented ciliary epithelium of the pars plana and pars plicata, as well as in ciliary body musculature. Weak Ngb and Cygb-IR was detected in the lens epithelium. Ngb and Cygb distribution was consistent between human and canine anterior segments and was co-localized within the same cells in all structures;Our studies are the first detailed description of Ngb and Cygb presence detected by immunohistochemical methods in different structures of the canine and human eye. Based on Ngb and Cygb localization and their previously reported biochemical features, we hypothesize that Ngb and Cygb may have important roles in scavenging reactive oxygen species and/or facilitating oxygen diffusion in the eye.