Analysis of cataractous and experimentally stressed lenses by 31P-NMR and other techniques shows significant changes in the concentrations of small, acid_soluble organic phosphate compounds (organic-P). Changes in lenticular organic-P may be diagnostic of early metabolic events in the formation of cataracts; however, the mechanisms of these changes are not understood. This laboratory has found that the stress-related decrease of lenticular P-choline, an intermediate in phospholipid (P-lipid) and membrane biosynthesis, results from four competing processes. Following osmotic or oxidative stress, P-choline leaks from the lens, its synthesis decreases, and both its hydrolysis and its utilization ( for P-lipid synthesis) increase. It is proposed to study P-choline as a model organic-P, to quantify its synthesis leakage, hydrolysis, and utilization to fully account for its decreased concentration in cataractous lenses and in lenses subjected to osmotic stress (diabetic rats or rat lenses cultured in 30 mM xylose or galactose) or to oxidative stress (culture with H202 or with photosensitizers and light). It is also proposed to compare the changes in P-choline with changes in other organic-P compounds to determine whether the mechanisms which affect P-choline may also affect structurally-similar, metabolically related compounds. HPLC and other very sensitive techniques will be used to quantify the changes in several organic-P compounds in oxidatively and osmotically-stressed lenses, with emphasis on compounds involved in membrane turnover. Radiotracer techniques will be used to measure changes in lens permeability toward organic-P compounds and to study changes in their metabolism. Incorporation of P- choline, P-ethanolamine, and other precursors into P-lipids will be quantified and compared to determine whether the observed increase in P-choline utilization is an isolated event or whether synthesis of several P-lipids change in parallel as might be expected membrane repair. Also, the ability of lenses to recover normal permeability of transport properties will be measured following damage by various amounts of exposure to transient osmotic and oxidative stress. The results of these studies will significantly increase our understanding of the response of lenses to cataractogenic stress and the effects of stress on a v vital class of biological compounds.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY007938-02
Application #
3265025
Study Section
Visual Sciences A Study Section (VISA)
Project Start
1989-01-01
Project End
1993-12-31
Budget Start
1990-01-01
Budget End
1990-12-31
Support Year
2
Fiscal Year
1990
Total Cost
Indirect Cost
Name
University of Tennessee Health Science Center
Department
Type
Schools of Medicine
DUNS #
941884009
City
Memphis
State
TN
Country
United States
Zip Code
38163
Jernigan Jr, Howard M; Blum, Penny S; Chakrabarti, Ipsit et al. (2005) Effects of cataractogenesis on the CDP-choline pathway: increased phospholipid synthesis in lenses from galactosemic rats and 13/N guinea pigs. Ophthalmic Res 37:7-12
Liu, Ying; Blum, Penny S; Pabst, Diana M et al. (2003) 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. Ophthalmic Res 35:185-91
Liu, Y; Ekambaram, M C; Blum, P S et al. (1998) Galactosemic cataractogenesis disrupts intracellular interactions and changes the substrate specificity of choline/ethanolamine kinase. Exp Eye Res 67:193-202
Jernigan Jr, H M; Zigler Jr, J S; Liu, Y et al. (1998) Effects of xylose on monkey lenses in organ culture: a model for study of sugar cataracts in a primate. Exp Eye Res 67:61-71
Ekambaram, M C; Jernigan Jr, H M (1994) Rat lens choline and ethanolamine kinases: independent kinetics in intact tissue-competition in homogenates. Biochim Biophys Acta 1213:289-94
Jernigan Jr, H M; Ekambaram, M C; Blum, P S et al. (1993) Effect of xylose on the synthesis of phosphorylcholine and phosphorylethanolamine in rat lenses. Exp Eye Res 56:291-7
Jernigan Jr, H M; Desouky, M A; Geller, A M et al. (1993) Efflux and hydrolysis of phosphorylethanolamine and phosphorylcholine in stressed cultured rat lenses. Exp Eye Res 56:25-33
Desouky, M A; Geller, A M; Jernigan Jr, H M (1992) Effect of osmotic stress on phosphorylcholine efflux and turnover in rat lenses. Exp Eye Res 54:269-76
Jernigan Jr, H M (1990) Metabolism of glutamine and glutamate in human lenses. Exp Eye Res 50:597-601