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Impressum
Antioxidant activity in porcine retina - dependence on iris pigmentation
1Nau-Staudt K., 2Nau W. M., 1Wunderlich K., 1Haefliger I. O., 1Flammer J.
1University Eye Hospital, 2Institute of Physical Chemistry, University of Basel, Switzerland
Objective: Lipid peroxidation in porcine irises has recently been
demonstrated to depend inversely on their degree of pigmentation. In humans
there is an inverse relation between the pigmentation of the iris and
the risk for age-related macular degeneration. We have now investigated
lipid peroxidation in porcine retinas in dependence on the degree of the
iris color.
Methods: The same number of retinas isolated from porcine eyes
with light blue (retina-blue) and dark brown iris (retina-brown, visual
selection) were placed (1:10 w/v) in buffer (50 mmol/l phosphate buffer
and 4 mmol/l sodium azide) in absence and presence of 50 µmol/l
butylated hydroxytoluene (BHT), an antioxidant. Equal volumes of homogenate
were taken and incubated at room temperature in duplicate for 5 - 80 min.
The amount of lipid peroxidation was assayed by the thiobarbituric acid
(TBA) test and additionally by the methylphenylindole-based lipid peroxidation
assay. Tissue tocopherol analysis was performed by the method of Taylor.
Protein concentration was measured by the method of Lowry.
Results: Homogenization induced lipid peroxidation. BHT reduced
lipid peroxidation in retinas to the amount previously measured in irises.
In retinas-brown, lipid peroxidation was markedly reduced (0.91 ±
0.21 nmol (MDA+4-HNE) / mg protein) in absence of BHT compared to retinas-blue
(1.42 ± 0.19 nmol (MDA+4-HNE) / mg protein, n=4, p<0.0001, 10
min). This significant effect was observed over 80 min time span. Similar
results were obtained with the thiobarbituric acid assay.
Conclusions: There is a stronger induction of lipid peroxidation
in retinasblue compared to retinas-brown. Presumably, this effect can
be attributed to a positive correlation of the antioxidant activity of
retina and iris.
Support: Deutsche Forschungsgemeinschaft (NA 361/1-1, Bonn, Germany) and
Swiss National Science Foundation Grant #32-52058 (Bern, Switzerland).