Abstract
Purpose::
To demonstrate the cellular distribution of immunoreactive glutamate (Glu), high affinity Glu transporter (GLAST) and glutamine (Gln) synthetase (GS) in human and monkey anterior uveal tissue in an effort to define physiological mechanisms that could explain how the paracellular pathway of the blood-aqueous barrier may be regulated by modulation of extracellular Glu.
Methods::
The immunofluorescent antibody technique was used to detect the co-localization of immunoreactive Glu, GLAST and GS in sections of human and monkey anterior uveal tissue.
Results::
Immunoreactive Glu was detected in human and monkey iris melanocytes, posterior iris pigment granule containing epithelial cells and in vascular endothelial cells and lymphocytes, as well as the pigmented and non-pigmented epithelial cells and muscle cells of ciliary body. Glu was concentrated in GLAST positive anterior iris melanocytes and posterior iris dilator muscle cells. Glu was highly concentrated at the apical side of GLAST, GS positive non-pigmented epithelial (NPE) cells of the pars plicata and at the apical surface of the columnar NPE cells of the pars plana ciliary body tissue.
Conclusions::
Immunoreactive Glu was detected in human and monkey iris melanocytes, ciliary body epithelial cells, vasculature endothelial cells, and iris and ciliary body muscle cells. The high concentration of Glu at the apical surface of GLAST, GS positive NPE cells suggest active Glu uptake by GLAST coupled to intracellular conversion of Glu to Gln by GS. The results support the idea that GLAST and GS activity could play important roles in modulating extracellular Glu and the permeability function of the blood-aqueous barrier.
Keywords: ciliary body • anterior segment • uvea