Physical Properties of Lens Membranes in Animals with Different Lifespans.

The lipid composition of eye lens fiber cell membranes varies among species, and these differences increase as a function of lifespan. However, the way in which the lipids of the fiber cell membranes are organized in different animals has not yet been studied in detail. This study compares how the structure, properties, and organization of lipids change during the lifespan of the mouse, pig, and human. These species were chosen because of the wide range of lifespans and significant differences in lipid composition. Models were made of phospholipid compositions resembling those of the lens fiber cell membranes of a mouse, pig, and human aged of 3, 23, and 70 years, respectively. To separate the effects of phospholipids and cholesterol, membranes were investigated for samples without cholesterol, with a cholesterol content close to the cholesterol saturation limits, and with a cholesterol content close to the cholesterol solubility thresholds. Membrane physical properties were obtained using EPR spin labeling methods. No significant differences in the physical properties of the membranes of any of the models were detected for membranes without and those in the presence of a saturating cholesterol concentration. Thus, not only cholesterol but also the appropriate phospholipid composition is a significant factor in maintaining eye lens homeostasis.