Document Detail

Effect of xylose on the synthesis of phosphorylcholine and phosphorylethanolamine in rat lenses.
MedLine Citation:
PMID:  8472784     Owner:  NLM     Status:  MEDLINE    
Choline, an essential phospholipid precursor, enters the lens by a facilitated transport system and is phosphorylated to form phosphorylcholine (P-choline). Intact lenses incubated with [3H]choline accumulate both [3H]choline and P-[3H]choline. The rate and extent of this accumulation have been used to study the effects of osmotic or oxidative cataractogenic stress, and also to test the ability of compounds to protect lenses from stress-related damage. The initial effect of oxidative stress on choline metabolism is decreased choline transport, but the mechanism by which osmotic stress affects the accumulation of [3H]choline is not understood. The effects of osmotic and oxidative stress on choline influx and metabolism were compared in rat lenses incubated in TC-199 medium. After osmotic stress by incubation with 30 mM xylose for up to 24 hr, lenses accumulated the same amount of radiolabel as controls during a 30 min pulse with [3H]choline. However, if the lenses were exposed to [3H]choline for 6 hr so that accumulation of radiolabel in the lenses was limited by the rate of P-choline synthesis, xylose treated lenses accumulated less choline than controls. Separation of the lenticular radiolabel into [3H]choline and P-[3H]choline confirmed that xylose decreased synthesis of P-choline, although adequate unphosphorylated [3H]choline was available in the lenses. A decrease in P-[3H]ethanolamine synthesis was also seen in xylose-treated lenses incubated with [3H]ethanolamine. Ethanolamine can enter lenses by a non-saturable process which is not dependent upon a transporter. Although xylose decreased P-choline synthesis in intact lenses, neither xylose nor xylitol inhibited choline kinase in lens homogenates.(ABSTRACT TRUNCATED AT 250 WORDS)
H M Jernigan; M C Ekambaram; P S Blum; M S Blanchard
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Experimental eye research     Volume:  56     ISSN:  0014-4835     ISO Abbreviation:  Exp. Eye Res.     Publication Date:  1993 Mar 
Date Detail:
Created Date:  1993-05-18     Completed Date:  1993-05-18     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0370707     Medline TA:  Exp Eye Res     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  291-7     Citation Subset:  IM    
Department of Biochemistry, University of Tennessee, Memphis 38163.
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MeSH Terms
Aminoisobutyric Acids / metabolism
Biological Transport, Active / drug effects
Choline / metabolism
Choline Kinase / metabolism
Ethanolamines / metabolism*
Lens, Crystalline / metabolism*
Organ Culture Techniques
Osmotic Pressure
Phosphorylcholine / metabolism*
Rats, Sprague-Dawley
Reactive Oxygen Species / metabolism
Time Factors
Xylose / pharmacokinetics
Grant Support
Reg. No./Substance:
0/Aminoisobutyric Acids; 0/Ethanolamines; 0/Reactive Oxygen Species; 0/Xylose; 107-73-3/Phosphorylcholine; 1071-23-4/phosphorylethanolamine; 141-43-5/Ethanolamine; 62-49-7/Choline; EC Kinase

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