UPTAKE OF DOCOSAHEXAENOIC ACID BY MICROVESSELS FROM DEVELOPING RAT-BRAIN

Uptake of polyunsaturated fatty acids by the rat brain occurs mainly d uring the three weeks before weaning. Docosahexaenoic acid [22:6], the predominant polyunsaturated fatty acid in the adult brain, appears to be preferentially taken up from the circulation by both the adult and developing rat brain. To test the hypothesis that this preferential i ncorporation was mediated by the cerebral microvasculature, we compare d the incorporation of 22:6 to a saturated fatty acid, palmitic acid [ 16:0], in freshly isolated rat brain microvessels from the pooled brai ns of entire litters of two-week-old rats (n=8 litters). For each litt er duplicate incubations with 2 muCi of [1-C-14]22:6 or [1-C-14]16:0 w ere performed in 60% autologous rat serum for 2 hr at 37-degrees-C. [H -3]Sucrose was included in each incubation, allowing correction for no n-specific uptake and trapping. An average of 2.7 +/- 2.0% (SD) of the radioactivity from 16:0 was found in the microvessels after 2 hr, vs 0.9 +/- 0.6% for 22:6. This yielded a three-fold enrichment of 16:0 ov er 22:6 (P=0.02, paired t-test). There was preferential incorporation of 22:6 into phosphatidylethanolamine and of 16:0 into phosphatidylcho line, although most of the label from either substrate remained as fat ty acid after the 2 hr incubation. These results do not indicate that brain capillaries mediate the preferential incorporation of polyunsatu rated fatty acids into brain tissue that was seen in intact young rats .