Phosphorylcholine and phosphorylethanolamine concentrations in the lens

Abstract

Phosphorylcholine and phosphorylethanolamine are precursors of phosphatidylcholine, sphingomyelin and phosphatidylethanolamine, the principal phospholipids of lens membranes. The present study compares the concentrations of phosphorylcholine and phosphorylethanolamine in rat, rabbit, chicken and human lenses. In lenses of adult animals phosphorylcholine concentrations ranged from a high of 11·1 m m in rats to a low of 0·12 m m in chickens; phosphorylethanolamine ranged from 1·7 m m in rats to 0·10 m m in chickens. The effects of age were studied in rabbit and chicken lenses. Both species showed an age-dependent decrease in the concentrations of both substances, although the absolute amounts per lens remained almost constant. In vitro incubation of rat lenses for 4 hr did not significantly change the intralenticular concentrations of either substance even when 1 m m choline was added to the medium. This demonstrates the suitability of the culture conditions for studies of choline transport and phospholipid metabolism. Finally, six cataractous human lenses were examined. Of these, five showed lower than normal concentrations of phosphorylcholine and phosphorylethanolamine. The only exception was classified as a posterior subcapsular cataract with slight cortical involvement.