DISTRIBUTION OF MEMBRANE PHOSPHOLIPIDS IN THE RABBIT UVEA

Background and Aims. Since the uveal tract becomes involved in inflamm atory disorders, which are known to affect lipid metabolism, we studie d normal membrane phospholipids (PLs) in order to (1) determine baseli ne PL profiles of the iris, ciliary body, and choroid, and (2) compare and contrast PL profiles of the uveal tissues. Methods. Iris, ciliary body and choroid tissues were isolated from rabbit eyes (n = 30) and extracted with chloroform-methanol using a modified Folch procedure. Q uantitative tissue PL profiles were obtained using P-31 nuclear magnet ic resonance. Results. Fourteen PLs were detected and quantitated in a ll three uveal tissues among which was one unidentified PL at -0.17 pp m. The five major PLs in the iris, ciliary body and choroid, respectiv ely, have the following PL composition (mole percent of total phosphor us): ethanolamine plasmalogen 14.58, 15.07, 16.52; phosphatidylethanol amine 13.10, 12.40, 9.23; phosphatidylserine 11.24, 10.27, 12.13; sphi ngomyelin (SM) 11.10, 11.97, 18.21; and phosphatidylcholine (PC) 36.61 , 36.70, 29.88. Additionally, lysophosphatidic acid, phosphatidic acid , lysophosphatidylcholine, phosphatidylinositol, and PC plasmalogen or alkacyl PC were detected in all tissues. Sphingosylphosphorylcholine also was detected in the ciliary body and choroid. Lysophosphatidyleth anolamine was detected in the choroid. In addition, 42 PL metabolic in dexes were calculated from these data, which permitted pathway-specifi c lipid analyses. Conclusion. This study establishes baseline PL profi les of the uveal tract tissues and will permit comparisons with tissue s from eyes with inflammatory disorders. The PL concentrations in conj unction with the indexes demonstrate that overall the choroid has memb ranes that are less permeable to ion translocation than either the iri s or the ciliary body, although there are compensatory concentration c hanges between the SM and PC components among these three tissues.