Figure 3. Hydrogen sulfide–attenuated glial fibrillary acidic protein expression and increased heat shock protein (HSP)-90 expression in retinal tissue. Effect of hydrogen sulfide (H₂S) preconditioning on retinal glial fibrillary acidic protein (GFAP; A) and HSP-90 (B) expression. A: Cross-sections of the retinas 7 days after unilateral ischemia/reperfusion (I/R) injury. In controls with and without H₂S preconditioning, GFAP was only positive in Müller cells and astrocytes in the ganglion cell layer (GCL). After ischemia, GFAP was upregulated in Müller cells. Their processes, extending through all retinal layers, became strongly GFAP positive. This upregulation seemed to be stronger in the I/R injury + room air group. The scale bar represents 50 µm. B: In nonpreconditioned eyes (control and ischemic), retinal HSP-90 expression remained at the baseline level. H₂S preconditioning in control eyes significantly increased HSP-90 expression. H₂S inhalation before I/R injury significantly induced retinal HSP-90 expression compared with I/R injury alone (***p<0.001). Data are presented as mean±SD of eight experiments.