Impact of aging and hyperbaric oxygen in vivo on guinea pig lens lipids and nuclear light scatter

PURPOSE. To measure lipid compositional and structural changes in lenses as a result of hyperbaric oxygen (HBO) treatment in vivo. HBO treatment in vi vo has been shown to produce increased lens nuclear light scattering. METHODS. Guinea pigs, approximately 650 days old at death, were given 30 an d 50 HBO treatments over 10- and 17-week periods, respectively, and the len ses were sectioned into equatorial, cortical, and nuclear regions. Lipid ox idation, composition, and structure were measured using infrared spectrosco py. Phospholipid composition was measured using P-31-NMR spectroscopy. Data were compared with those obtained from lenses of 29- and 644-day-old untre ated guinea pigs. RESULTS. The percentage of sphingolipid approximately doubled with increasi ng age (29-544 days old). Concomitant with an increase in sphingolipid was an increase in hydrocarbon chain saturation. The extent of normal lens lipi d hydrocarbon chain order increased with age from the equatorial and cortic al regions to the nucleus. These order data support the hypothesis that the degree of lipid hydrocarbon order is determined by the amount of lipid sat uration, as regulated by the content of saturated sphingolipid. Products of Lipid oxidation (including lipid hydroxyl, hydroperoxyl, and aldehydes) an d lipid disorder increased only in the nuclear region of lenses after 30 HB O treatments, compared with control lenses. Enhanced oxidation correlated w ith the observed loss of transparency in the central region. HBO treatment in vivo appeared to accelerate age-related changes in lens lipid oxidation, particularly in the nucleus, which possesses less antioxidant capability. CONCLUSIONS. Oxidation could account for the lipid compositional changes th at are observed to occur in the lens with age and cataract. Increased lipid oxidation and hydrocarbon chain disorder correlate with increased lens nuc lear opacity in the in vivo HBO model.