Effect of Osmotic Stress on Phosphorylcholine Efflux and Turnover in Rat Lenses

Lipids and the ocular lens

“…Changes in the synthesis of phospholipids and their precursors during cataractogenesis have been investigated, but further studies are necessary to determine if the changes are related to natural differences in phospholipid metabolism or if these alterations are the result of damageinduced pathways that lead to membrane repair ( 179 ). The concentrations and rates of synthesis of phosphorylcholine and phosphoethanolamine, precursors of phospholipid synthesis decrease in cataractogenesis and cataractogenic stress (180)(181)(182)(183)(184)(185)(186)(187)(188)(189)(190)(191), and the kinetic properties and substrate specifi city of choline/ethanolamine kinase change during galactosemic cataractogenesis ( 192 ). Increased phospholipid synthesis was reported to occur in an aldose-reductase inhibitor cataract model ( 185 ).…”

Effects of Cataractogenesis on the CDP-Choline Pathway: Changes in ATP Concentration and Phosphocholine Synthesis during and after Exposure of Rat Lenses to Sugars in vitro and in vivo

“…Aliquots of each TCA supernatant were counted to determine the amount of [ 3 H]choline that had entered each lens. Using methods previously described [10,17], a second aliquot of each TCA supernatant was enzymatically analyzed for [ATP], and P-Cho was separated from choline by ion exchange chromatography of the ATP assay mixture on Dowex 1-X8, 200 to 400-mesh resin (OH -form) and counted to measure synthesis of P-[ 3 H]Cho (i.e. phosphorylation of [ 3 H]choline).…”

Effects of Xylose on Monkey Lenses in Organ Culture: A Model for Study of Sugar Cataracts in a Primate

“…Xylose was purchased from Fisher Scientific Co. (Fair Lawn, NJ, U.S.A.). Dowex 1-X8-400-Cl − was converted to the OH − form as previously described (Desouky et al, 1992). Powdered TC-199 culture medium mix and other biochemicals were obtained from Sigma Chemical Co. (St Louis, MO, U.S.A.).…”

“…Finally, the lenses were homogenized in 2 ml of 6 % TCA. Each TCAinsoluble pellet was extracted and counted to measure the amount of $H incorporated into P-lipids, and aliquots of each medium and TCA supernatant were analysed for [$H]choline and P-[$H]choline (Desouky et al, 1992). The transfer of choline or P-choline from the lenses into the medium will be referred to as efflux or ' leakage '.…”

“…For example, culture of lenses with the cataractogenic sugar xylose has been shown to cause xylitol accumulation and to affect transparency, hydration, membrane permeability, electrolyte and metabolite concentrations, protein synthesis, lipid peroxidation, and membrane transport of ions and metabolites (Obazawa et al, 1974 ;Thomas, Mahendroo and Lou, 1988 ;Desouky, Geller and Jernigan, 1992 ;Jernigan et al, 1993 ;Ohta et al, 1996 ;Kamiya and Zigler, 1996). Unfortunately, the severely limited availability of suitable human lenses precludes their use for most organ culture studies.…”