Stearate desaturase in rat brain and liver.
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Biomedical subjects
Publications and source records attributed to H Debuch.
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The uptake of 14C labelled alkyl chains into the alkenyl chains of plasmalogens was estimated 12, 24, 48 and 72 h after intracerebral administration of different substrates to 14 day-old rats We used as substrates 1-[1-14C] alkyl-3-sn-glycerophosphoethanolamines, containing in the 2-position of the glycerol residue a stearoyl (substrate I), an oleoyl (II), an archidonoyl (III), a 4, 7, 10, 13, 16, 19-docosahexaenoyl (IV) or no acyl residue (substrate V, so-called lysoether phosphatide). 1) If the fatty acid in the 2-position of the substrate is a saturated one (as in experiment I), the recovery of radioactive alkyl chains is relatively high, but their desaturation is very slow and seems not to reach its maximum even after 72 h. 2) If a substrate with an unsaturated fatty acid in the 2-position is applied, the number of radioactive chains (alkyl plus alkenyl) depends on the chain length and/or the number of double bonds in the fatty acids. The desaturation of the alkyl chains, however, reaches its maximum about 48 h after application (except for substrate IV). 3) Not only is the recovery of radioactivity in the glycerophosphoethanolamine lipids by far the highest in experiment V at any time, but also the total activity of the alkenyl chains has already reached a maximum 24 h after application.
Rats were treated with triton, dextran, silver and iron. The lysosomal fractions from their livers were isolated and the lipids analysed. (MAG)2P could be detected in every phospholipid fraction, accounting for 6-28 per cent of the total lipid phosphorus. The composition of the fatty acids from this acidic glycerophospholipid shows an extraordinarily high amount of polyenoic fatty acids (58-82 per cent of the total), of which docosahexaenoic acid is a main compound.
Tissue slices from the liver and brain of 7-day-old rats incubated with [1-14C]stearic acid desaturate the stearate to oleate. The activities of the two tissues are different but of the same order of magnitude. With increasing age, the activity in the liver increases markedly, while the brain activity decreases. The postmitochondrial supernatant from adult (3-month-old) liver contains 2 to 3 orders of magnitude more stearoyl-CoA dehydrogenase activity than the brain postmitochondrial fraction. The washed microsomal fraction from liver had about the same activity as the postmitochondrial supernatant, but no dehydrogenase activity could be detected in the washed microsomal fraction from the brain. The acyl-CoA synthetase and the palmitoyl-CoA hydrolase activities measured in the washed microsomes from adult brain were both lower than in liver microsomes. The concentration of stearoyl-CoA (the substrate for the stearoyl-CoA dehydrogenase) resulting from the ratio of these activities was too high, however, for the lack of desaturase activity to have been simulated by lack of substrate.
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