Transport of 22:6n-3 in the plasma and uptake into retinal pigment epithelium and retina.
Vertebrate retina is highly enriched in 22-carbon polyunsaturated fatty acids (PUFAs), especially docosahexaenoic acid (DHA, 22:6n-3), which is supplied by the plasma. To study the transport and uptake of 22:6n-3 into the retina, young Long Evans rats were fasted overnight and given an oral dose of palm oil containing [4,5-3H] 22:6n-3 and [9,10-3H] 18:1n-9 (oleic acid). At 1, 6, 12, 24, and 48 hr postgavage, blood, liver, retinal pigment epithelium (RPE) and retina were collected, and plasma lipoprotein fractions were obtained by density-gradient ultracentrifugation. The distribution of radioactivity among the different lipoproteins (dpm%) showed that both fatty acids were mainly associated with VLDL 1 hr after gavage. For 22:6n-3, the majority of radioactivity was associated with LDL at 6 hr postgavage. By 12 hr post administration, the majority of radioactivity was in HDL2 which retained around 40% until the 48-hr time point. For 18:1n-9, a different profile was observed. By 6 hr postgavage, approximately 30% of the radioactivity was found in HDL2, but the percentage of radioactivity decreased to approximately 20% thereafter. The half-life of 22:6n-3 was significantly longer than for 18:1n-9 (P < 0.0005) in plasma, liver, and the lipoprotein fractions. The specific activities of 22:6n-3 and 18:1n-9 in the plasma continuously declined from 1 hr to 48 hr postgavage, while liver showed a peak of specific activity at 6 hr, then gradually declined.(ABSTRACT TRUNCATED AT 250 WORDS)
Wang
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Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030.
Anderson
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D000818:Animals; D001693:Biological Transport, Active; D004281:Docosahexaenoic Acids / Q000097:blood*; D008074:Lipoproteins / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D009829:Oleic Acids / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012160:Retina / Q000378:metabolism*; D013997:Time Factors
D008074:Lipoproteins; D009829:Oleic Acids; D004281:Docosahexaenoic Acids