Possible role of the choroid plexus in the supply of brain tissue with polyunsaturated fatty acids.

Delta-6 desaturase was measured in rat brain microvessels and choroid plexus by incubation in the presence of radioactive linoleic acid. Under our conditions, in 21-day-old animals, delta-6 desaturase was not detected in brain microvessels. In contrast, it was present in choroid plexus (about 21 pmol/min per mg protein). In comparison, the activity in brain was much lower (about 1 pmol/min per mg protein) and higher in liver (about 55 pmol/min per mg protein). Interestingly, during development the activity in choroid plexus peaked at day 6 after birth and declined slightly thereafter. The pattern of incorporation of linoleic acid radioactivity was not the same in choroid plexus and microvessels. These results show that delta-6 desaturase was not detected in brain microvessels but was present in choroid plexus.