Biochemical and Ultrastructural Changes in lens during Aging of Wistar Albino Rats

Aims: To correlate the age-related structural changes in lens with its contents of amino acids and minerals involved in its functional activity (sodium, calcium, magnesium and copper).
Study Design: Experimental study.
Place and Duration of Study: Department of Zoology, Faculty of Science, Mansoura University, Egypt, between June 2009 and July 2011.
Methodology: One hundred male and female albino rats of the Wistar strain (Rattus norvegicus) aging 1, 6, 18, 30 & 42 months were used during experimentation. At the mentioned ages, the animals were sacrificed by diethyl ether and ocular regions were dissected and lens separated. Amino acids content were determined in both lenses of five individuals. In the other five individuals, unilateral ectomized lenses were subjected for chemical determination of calcium, sodium, cupper and magnesium. The rest lenses on the other side were fixed in 10% phosphate buffered formalin followed by 2.5% glutaraldhyde for scanning electron microscopic investigation. Statistically analysis was carried out by the help of SPSS software.
Results: The estimated amino acids were altered in both sexes with advancement of aging. The lens amino acids; taurine, prolline, serine, threonine, methionine, lysine and arginine were markedly increased during aging comparing with apparent depletion of asparate, valine and methionine. The alterations in amino acid contents were parallel with increased accumulation of calcium, sodium and cupper and a depletion of magnesium content. Scanning Electron Microscopic (SEM) observations exhibited sequences of changes of the structures of lens fibers and their pattern of attachments during the advancement of aging. In the advanced aged group, the lens fibers become fragile and widely separated as a result of loosely attached of the interfibrillar junctions of the ball and socket especially at 30 & 42 month old rats.
Conclusion: Aging led to alterations of lens fibers at ultrastructural levels associated with diversity of changes in their amino acids contents parallel with increase accumulation of sodium, calcium and cupper and a decrease of magnesium content. The observed findings may be attributed to the increase of advanced glycation end products initiated oxidative stress, impairing lens structure and function.