This study was undertaken to determine whether there are age-related c
hanges in the specific activities of several glycosidases in fresh ret
inal pigment epithelial cells (RPE) isolated from the posterior pole o
f human donor eyes. One hundred and twenty-one pairs of eyes from huma
n donors, between the ages of 43 and 95 years, were obtained from the
National Disease Research Interchange (NDRI, Philadelphia, PA) and the
Cleveland Ohio Eye Bank within 18 to 24 h of death. None had historie
s of diabetes, hepatitis, HIV infection, intraocular surgery, or docum
ented age-related macular degeneration, although several older donors
with evidence of drusen were included in the study. RPE cells were iso
lated from the posterior third of the retina using the conventional ru
sh method and homogenized with a glass, Broeck tissue grinder. All pos
t-nuclear supernatants were anlayzed for glycosidase activity; a small
er number of nuclear pellets were assayed to verify that the majority
of the enzyme activity was associated with the post-nuclear sypernatan
ts. Glycosidase activity was quantitated fluorometrically by measuring
the enzymatic release of umbelliferone from synthetic substrate prepa
rations, specific for each enzyme. Total protein was determined by a m
icro BCA protein assay. Regression analysis revealed statistically sig
nificant age-related decreases for the specific activities of alpha-ma
nnosidase (p = 0.0001), beta-galactosidase (p = 0.0001), N-acetyl-beta
-glucosaminidase (p = 0.0001), and N-acetyl beta galactosaminidase (p
= 0.0001) in fresh human donor RPE cells taken from the region of the
posterior third of the retina that included the macula. Mannose and N-
acetyl-glucosamine are major carbohydrate monomers of the oligosaccari
de chains of human rhodopsin, and a realtively high percentage of the
oligosaccharide chains are galactosylated. Defects in their degradatio
n may lead to the accumulation of undigested residual material in the
RPE.