ONTOGENY OF LIPIDS IN CHICK-EMBRYO RETINA

Purpose. The effects of embryonic development on lipid composition in the retina were studied in 7, 11, 15, and 18-day-old chick embryos and newly hatched chicks. Methods. The proportions of phospholipids, free and esterified cholesterol, diacylglycerides, and free fatty acids we re determined using the Iatroscan TLC/FID procedure. Gas chromatograph y and mass spectrometry were used to determine the fatty acid composit ion. Results. The major phospholipid species were phosphatidylethanola mine, phosphatidylcholine, phosphatidylserine, phosphatidylinositol, l ysophosphatidylcholine, and sphingomyelin. Concentrations of the analy zed components have been related to the chronology of concrete stages of retinal development. The fatty acid composition of the total lipids , (n-6):(n-3) and saturated:unsaturated fatty acid ratios, and other p arameters are reported. The proportions of total saturated and total m onounsaturated fatty acids decreased very little from day 7 to hatchin g, whereas total polyunsaturated fatty acids nearly doubled over the s ame period. The increase in C18:2(n-6) from day 11 onwards was not fol lowed by a similar increase in C20:4(n-6), hence the C20:4 to C18:2 ra tio decreased with age. Conclusions. The cholesterol:phospholipid rati o decreased from day 7 to day 15 and increased from day 15 to hatching . High proportions of esterified cholesterol, very probably originatin g in the retinal pigment epithelium, were also recorded. Total saturat ed and monounsaturated fatty acids decreased, while polyunsaturated fa tty acids increased during the period of initial retinal growth.