Abstract
Purpose::
To demonstrate the cellular distribution of immunoreactive glutamate (Glu) and sodium-dependent high affinity excitatory amino acid transporters (EAAT) of Glu; GLAST (EAAT-1), GLT-1 (EAAT-2) and EAAC-1 (EAAT-3) in monkey corneal epithelial cells.
Methods::
The immunofluorescent antibody technique was used to detect immunoreactive Glu, GLAST, GLT-1 and EAAC-1 in sections of corneal tissue from 2 rhesus monkeys.
Results::
The immunoreactivity of Glu and GLT-1, GLAST and EAAC-1 in stromal cells of the cornea was less well defined and much less than in the epithelial cells. Immunoreactive Glu was detected within the cytoplasm of the inner 3 layers of the stratified epithelial cells in monkey corneas and was highly concentrated at the basal surface of some corneal epithelial cells in the first stratified layer. In addition, immunoreactive Glu was detected within Bowman’s membrane along the basal surface of the corneal epithelial cells. GLAST, GLT-1 and EAAC-1 were detected in the basal layer (i.e., inner most layer resting on Bowman’s membrane) of stratified squamous epithelial cells. The expression of GLT-1 appeared to be higher than GLAST and EAAC-1. Notably, the third and fourth epithelial cell layers were almost devoid of EAATs, while EAAC-1 was detected in the second level of stratified epithelial cells. Curiously, GLAST, GLT-1 and EAAC-1 were detected on large flat squamous epithelial cells on the corneal surface, but only GLAST was detected on monkey corneal stromal fibroblasts.
Conclusions::
Immunoreactive Glu was detected in monkey corneal epithelial and stromal cells. The high concentration of Glu at the apical surface of EAAT (GLAST, GLT-1 and EAAC-1) positive corneal epithelial cells next to Bowman’s membrane supports active Glu transport by corneal cells.
Keywords: cornea: epithelium • metabolism • protein structure/function