Interspecies comparisons of lens phospholipids

The purpose of this study was to compare and contrast quantitative crystalline lens phospholipid profiles among human, pig, rabbit, rat mouse, dog, lamb, guinea pig, beef, calf, chinook salmon, and golden roach. Lenses were extracted using chloroform-methanol. The extracts were prepared for phospholipid 31P NMR quantitative analysis using an NMR analytical reagent specifically designed for this purpose. Lens phospholipid profiles vary among vertebrate species. Thirteen different phospholipids [phosphatidylglycerol, lysophosphatidylethanolamine, phosphatidic acid, diphosphatidylglycerol, the ethanolamine plasmalogen (EPLAS), phosphatidylethanolamine (PE), phosphatidylserine (PS), sphingomyelin (SM), lysophosphatidylcholine, phosphatidylcholine (PC), including four uncharacterized (unknown) phospholipids at 1.31 ppm (human), 1.20 ppm (human, rabbit, dog, lamb, beef, calf), 0.13 ppm (all except rat), and -0.17 ppm (rat, beef) were detected. EPLAS, PE, PS, SM, and PC are the major lens phospholipids in all species except the human, where the major phospholipid is the unknown at 0.13 ppm. The lens content of this major unknown in mole percentage of the total detected phospholipid profile is: human 43.7; pig 6.7; rabbit, 6.1; rat (not detected); mouse, 3.2; dog, 5.0; guinea pig, 2.0; lamb, 7.0; beef, 7.7; calf, 5.6; chinook salmon, 6.7; and golden roach, 1.6. Large qualitative and quantitative differences were observed among lens species, indicating the necessity for prudent selection of appropriate animal models. The most striking finding is that no other species except the human species exhibits such a profound amount of the unknown phospholipid at 0.13 ppm. In the human lens, this phospholipid is the major phospholipid.