462
BIOCHEMICAL SOCIETY TRANSACTIONS
pathway, and the monoenoic species by acylation of glycerol 3-phosphate. The monoenoic species of phosphatidylinositol may be largely synthesized de nouo from the
corresponding species of phosphatidic acid, but the other species may be derived by a
combination of synthesis de nouo and transacylation reactions involving the monoenoic
phosphatidylinositol.
Luthra, M. G . & Sheltawy, A. (1972~)Biochem. J. 126, 1231-1239
Luthra, M. G. & Sheltawy, A. (19726) Biochem. J. 128, 587-595
The Incorporation of Lholeate and Arachidonate into Liver and
Brain Lipids of Developing Rats
A. J. SINCLAIR and M. A. CRAWFORD
Nuffeld Institute of Comparative Medicine, The Zoological Society of London, Regent's
Park, London NW1 4RY, U.K.
Linoleate and linolenate are fatty acids produced by green plants; however, they cannot
be synthesized in significant amounts by animals. In animals dietary linoleate and linolenate are converted into longer-chain and more-unsaturated fatty acids. The fatty
acids of the linoleate and linolenate series are consistently found in the structural lipids
of animal cells.
It has been assumed that most of the C20-C22polyenoic fatty acids in the body originate from the metabolism of dietary linoleate (C18:2)and linolenate (C18:3), and little
attention has been paid to dietary longer-chain polyenoic fatty acids. It is known that
certain foods are rich in these fatty acids (e.g. chicken, veal and fish), and animal experiments have shown that dietary arachidonate and docosahexaenoate can be incorporated
into tissue lipids (Brenner & JosB, 1965; Mohrhauer & Holman, 1963).
Long-chain polyenoic fatty acids are of particular interest in relation to the brain,
since this is a tissue that contains large amounts of C20;4, C22:4 and C22:6fatty acids and
very little C18:2and C18:J fatty acids (Crawford & Sinclair, 1972). In the rat a significant
proportion of brain development occurs during the suckling period, and it is known
that more than 60% of the long-chain polyenoic fatty acids ( c 2 0 : 4 and C22:6)in the rat
brain are laid down by the end of the suckling period (Sinclair & Crawford, 1972a). It is
noteworthy that rat milk contains both linoleate and linolenate and also significant
amounts of their longer-chain metabolic products (Sinclak & Crawford, 1972~).
Since the bulk of Cz0:*and C22:6fatty acids in rat brain are laid down at a time when the
diet contains these fatty acids, we are interested in the possible role of dietary polyenoic
fatty acids in contributing to brain polyenoic fatty acids. To investigate this it is
necessary to know whether CzOZ4
and C22:6fatty acids can enter the developing rat brain.
We have recently shown this to be the case for the C22:6fatty acid (Sinclair & Crawford,
19726), and the present communication is concerned with the uptake of [l-14C]linoleate
and [3H]arachidonate by liver and brain lipids of 16-day old rats. Five pups were given
an oral dose of the radioactivity (14C+3H)and the pups were killed 22h later.
The results showed that a significantly greater percentage of the administered arachidonate was incorporated into the liver, brain and serum lipids compared with the linoelate incorporation. The 3H/14Cratios in the total lipids of the liver, brain and serum
were 8.8,3.7 and 14 respectively, compared with a ratio of 1.1 for the administered dose.
In the liver the triglycerides and phospholipids contained more than 90% of the total
lipid radioactivity. The W/14C ratio was 2.3 for the liver triglycerides, 22.3 for the liver
phospholipids and 4.2 for the brain phospholipids.
Isolation of the individual fatty acids by preparative g.1.c. showed that more than
80% of the 3H in the fatty acids of the liver triglycerides, phospholipids and brain
phospholipids was associated with the C20:ofatty acid. A different distribution of the 14C
radioactivity was observed: in the liver triglycerides and phospholipids 75 and 53%
respectively of the radioactivity in the fatty acids were associated with the
fatty acid
1973
534th MEETING, NOTTINGHAM
463
and less than 7 and 16% respectively with the longer-chain metabolites of linoleate. In
the brain phospholipid fatty acids 10%of the 14Cwas associated with the C18:2fatty acid,
17% with the longer-chain metabolites and more than 60% with saturated and monounsaturated fatty acids.
fatty acid in rat brain could be synthesized in the brain from the Ciaz2 fatty
The C20:4
acid or it could enter the brain as Cz0:.,fatty acid from the blood; synthesis in the brain
is unlikely, since the chain-elongation-desaturationenzyme activity is very low in the
developing rat brain (StrouvC-Vallet & Pascaud, 1971). Also, the results of the present
experiments show that, at a time when the brain is laying down c 2 0 : 4 fatty acid, this is a
more efficient precursor of brain CZOt4
fatty acid than is C18:2fatty acid. This opens the
question of the role of long-chain polyenoic fatty acids in the diet and particularly
their role in brain development.
Brenner, R. R. & JosB, P. (1965) J. Nutr. 85, 196-204
Crawford, M. A. & Sinclair, A. J. (1972) in Lipids, Malnutrition and the Developing Brain
(Elliott, K. & Knight, J., eds.), pp. 267-287, Associated Scientific Publishers, Amsterdam
Mohrhauer, H. & Holman, R. T. (1963) J. Lipid Res. 4, 151-159
Sinclair, A. 3. & Crawford, M. A. (1972~)J. Neurochem. 19, 1753-1758
Sinclair, A. J. & Crawford, M. A. (1972) FEBS Lett. 26, 127-129
Strouv6-Vallet, C. & Pascaud, M. (1971) Biochimie 53, 699-703
Turnover of Brain-Cortex Phospholipids and its Relation to
Endogenous Acetylcholine
LARS WIDLUND and EDITH HEILBRONN
Section of Biochemistry, Research Institute of National Defence, Department 1,
S-172 04 Sundbyberg 4, Sweden
Acetylcholine-stimulated incorporation of [32P]Piinto brain-cortex phospholipids is
higher with Sarin (isopropyl methylphosphonofluoridate) as an anti-cholinesterase than
with eserine (E. Heilbronn & L. Widlund, unpublished work). As uptake of acetylcholine
into slices occurs provided that the organophosphorus compound (Heilbronn, 1970;
Polak, 1969; Schubert & Sundwall, 1967) but not eserine (Polak, 1969; Schubert &
Sundwall, 1967) is the anti-cholinesterase, the increased incorporation of [32P]Pimight
be caused by a rise in the acetylcholine concentration within the nerve endings. Surprisingly, incorporation of [32P]Piinto phospholipids (mainly phosphatidic acid) of isolated
brain-cortex synaptosomes is not dependent on the nature of the anti-cholinesterase.
Although they are metabolically active and accumulate choline (against a concentration
gradient) (E. Heilbronn & L. Widlund, unpublished work), it seems rather doubtful
whether the synaptosomes take up acetylcholine.
Heilbronn, E. (1970) J. Neurochem. 17, 381-389
Polak, R. L. (1969) Brit. J . Pharmacol. 36, 144-152
Schubert, J. & Sundwall, A. (1967) J. Neurochem. 10, 807-812
Inhibition of Fatty Acid Synthesis in Central Nervous Tissue in
Phenylketonuria
JOHN M. LAND and JOHN B. CLARK
Department of Biochemistry, St. Bartholomew’s Hosp&z/ MedicaP College,
Charterhouse Square, London E C l M SBQ, U.K.
Phenylketonuria is an inborn ‘error of metabolism’ in which abnormally high concentrations of phenylalanine and some of its metabolic products, namely phenyl-lactate,
phenylpyruvate and hydroxyphenylacetate, are present in the plasma (Harris, 1959). It is
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