35S-methionine incorporation in rat lenses in media simulating cataractogenic conditions.

Lenses obtained from rats on a galactose diet for six days showed a marked reduction in their capacity to incorporate 35S-methionine into protein even though there was no reduction in the capacity of the lenses to incorporate 3H-thymidine and 3H-uridine into DNA and RNA, respectively. Therefore, lenses were incubated in media in which various putative cataractogenic factors were varied to determine the effects on 35S-methionine incorporation. Methionine incorporation paralleled the size of the AIB pool rather than the chloride ratio or concentration of potassium in the lens. The size of the amino acid pool and the concentration of lens potassium are known to be lowered by lens swelling. When the concentration of potassium in the lens is lowered, along with swelling in hypotonic medium or in medium containing galactose, or when the concentration of potassium is lowered with little swelling by substitution of choline for some of the sodium in the medium. 35S-methionine incorporation is decreased. However, this decrease in 35S-methionine incorporation was prevented in all cases without a significant increase in potassium concentration if the medium was fortified with amino acids. Increasing the level of potassium in the medium increased the concentration in the lens to normal levels. However, 35S-methionine incorporation was not increased in media containing galactose or choline.