UV laser photodamage to whole lenses

Lenses from rat or calf were exposed in vitro to UV radiation from a nitrogen laser operated at 337.1 nm or from an excimer laser operated at 3.8 nm. Visible light transmission was monitored during calf lens irradiations at 308 nm and found to decrease. Proteins were extracted from the irradiated rat or calf lenses, separated into water soluble and insoluble fractions, and analysed using SDS-PAGE. Comparison of these gels with dark controls showed that, following photolysis, there was loss of polypeptide material in the 20-30 kDa region and concomitant formation of polymers at 40 and 60 kDa, and at greater than 100 kDa in calf lens (308 nm irradiation) and rat lenses (337.1 nm irradiation) in vitro. In addition, there was evidence for formation of lower molecular weight polypeptides at 10 kDa in the protein from irradiated rat lenses. The rat SDS-PAGE gels were challenged against anti-calf gamma crystallin serum. There was clear evidence that the polymeric material, in the water insoluble protein fraction from the 337.1 nm photolyzed rat lenses was derived in part from gamma crystallin. The macromolecular changes detected in these photolyzed rat and calf lens proteins were similar to those previously reported to accompany aging in the human lens. Biochemical changes of the type observed in UV irradiated rat and calf lenses may be responsible for the loss of visible light transmission seen in calf lenses.