Photolysis of intact young human, baboon and rhesus monkey lenses

Intact young human, baboon and rhesus monkey lenses were subjected to near-UV irradiation under identical conditions and fluorophore buildup was continuously monitored for several hours. The compositional changes occurring in the lenses were monitored by analyzing the ethanol extracts of the irradiated and control lenses using high-performance liquid chromatography and thin-layer chromatography (TLC). The chromatograms of the supernatant detected at 365 nm as well as the TLC scans showed the presence of 3-hydroxykynurenine glucoside (3-HKG) and two other kynurenine-type compounds. The 3-HKG and one of the compounds were found in all three species, while the remaining one was structurally different in the lower primates. A loss of 3-HKG as a result of irradiation was apparent in all the lenses and correlated with the buildup of the blue fluorophore, suggesting that the latter may be a photoproduct(s) of 3-HKG. The kinetic analysis of baboon and human lenses showed a slowdown in the fluorophore buildup as irradiation times increased. This was probably due to the competitive absorptions of 3-HKG and other chromophores present. Rhesus monkey lenses did not exhibit this slowdown.