Changes in ferritin H- and L-chains in canine lenses with age-related nuclear cataract.
OBJECTIVE
To determine potential differences in the characteristics of the iron storage protein ferritin and its heavy (H) and light (L) subunits in fiber cells from cataractous and noncataractous lenses of older dogs.


METHODS
Lens fiber cell homogenates were analyzed by SDS-PAGE, and ferritin chains were immunodetected with ferritin chain-specific antibodies. Ferritin concentration was measured by ELISA. Immunohistochemistry was used to localize ferritin chains in lens sections.


RESULTS
The concentration of assembled ferritin was comparable in noncataractous and cataractous lenses of similarly aged dogs. The ferritin L-chain detected in both lens types was modified and was approximately 11 kDa larger (30 kDa) than standard L-chain (19 kDa) purified from canine liver. The H-chain identified in cataractous fiber cells (29 kDa) differed from the 21-kDa standard canine H-chain and from the 12-kDa modified H-chain present in fiber cells of noncataractous lenses. Histologic analysis revealed that the H-chain was distributed differently throughout cataractous lenses compared with noncataractous lenses. There was also a difference in subunit makeup of assembled ferritin between the two lens types. Ferritin from cataractous lenses contained more H-chain and bound 11-fold more iron than ferritin from noncataractous lenses.


CONCLUSIONS
There are significant differences in the characteristics of ferritin H-chain and its distribution in canine cataractous lenses compared with noncataractous lenses. The higher content of H-chain in assembled ferritin allows this molecule to sequester more iron. In addition, the accumulation of H-chain in deeper fiber layers of the lens may be part of a defense mechanism by which the cataractous lens limits iron-catalyzed oxidative damage.
Goralska
Malgorzata
M
Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, North Carolina 27606, USA. margaret_goralska@ncsu.edu
Nagar
Steven
S
Colitz
Carmen M H
CM
Fleisher
Lloyd N
LN
McGahan
M Christine
MC
D000375:Aging; D000818:Animals; D001052:Apoferritins / Q000378:metabolism*; D002386:Cataract / Q000378:metabolism / Q000662:veterinary*; D004283:Dog Diseases / Q000378:metabolism*; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel / Q000662:veterinary; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D007908:Lens, Crystalline / Q000378:metabolism*; D008856:Microscopy, Fluorescence / Q000662:veterinary
D001052:Apoferritins