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Y. Liu, Z. Lu, H. Gong; Comparative Studies of the Effect of Rho-Kinase Inhibitor,Y27632, on Bovine, Monkey and Human Outflow Pathways. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5721.
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Fresh enucleated bovine, monkey and human eyes were perfused at 15 mmHg to establish a baseline C. Experimental eyes (bovine: N=7, monkey: N= 4 and human: N = 4) were perfused with PBS+50 µM Y27 for 30 min, while control eyes (bovine: N=5, monkey: N= 4 and human: N=4) were perfused with PBS. All eyes were perfused with fluorescent microspheres (0.5µm; 0.002%) to label the outflow patterns before perfusion-fixation. Confocal images of frontal sections were taken along the IW of Schlemm’s canal (SC). The total length (TL) and the tracer-decorated length (L) of the IW were measured, and the average % effective filtration length (PEFL=L/TL) was calculated. Sections with SC were examined by light and electron microscopy. The TL of IW and the length exhibiting separation (SL) in the JCT were measured and analyzed. The relationship between C, outflow pattern, and morphology was compared in three species.
After Y27 treatment, C increased significantly in bovine (p=0.03) and monkey eyes (p=0.002) vs controls. No significant increases in C were found in human eyes (p=0.98). A more uniform tracer pattern was seen in Y27 treated than controls in bovine and monkey, while similar segmental distribution of tracer pattern was seen in both control and Y27 human eyes. The PEFL in Y27 eyes was 2-fold larger than controls (p=0.002) in bovine and 3.4-fold larger (p<0.001) in monkey eyes. No significant increase in PEFL was found in Y27 vs control human eyes (p=0.41). The percent SL was significantly increased in Y27 eyes compared to controls in bovine (p<0.001) and monkey (p=0.001). By electron microscopy, the separation was mainly between the basal lamina of the IW and JCT in bovine eyes and between JCT cells and JCT cells and matrix in monkey eyes. No discernable separations between the IW and JCT and in the JCT were found in Y27 treated human eyes vs controls. But in the area showing tracer labeling, the structure of the JCT was looser; while in area without tracer labeling, the JCT appeared compact.
Y27 significantly increased C and PEFL in bovine and monkey but not in human eyes under the same experimental conditions. Increase in C after Y27 treatment coincides with an increase in available area for aqueous outflow and greater separation between matrix, cells and cells and matrix in the JCT. The hydrodynamic changes are likely driven by structural changes in the JCT which may regulate C.
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