Age-related variations in the distribution of crystallins within the bovine lens

The native water-soluble proteins of equator, anterior cortex, posterior cortex and nucleus from bovine lenses in the age range 0·3–33·7 years were analyzed by high-pressure gel-permeation chromatography and high-pressure ion-exchange chromatography. Unlike the equator and cortices, the nucleus shows a gradual decrease in α-crystallin proportion with age which is not compensated for by an increase in HM-crystallin. The β H 6-crystallin species, almost the only β H-component in the youngest lens, is largely replaced by at least four fractions with higher and lower molecular weights in the older lenses. In the nucleus a β L-component (39 000 MW) increasingly seems to replace the major β L-crystallin ( β L 2, 50 000 MW). Moreover, a switch in the synthesis of monomeric crystallins is demonstrated. This study clearly reveals an age-related increase in the size heterogeneity of the native soluble crystallins with age.