5. DISTRIBUTION OF PHOSPHOLIPIDS
251
Among other phospholipids that have been reported in rat liver but are
not yet well characterized is one containing glutamic acid (92) and two
which have amino nitrogen: phosphorus : fatty acid ratios of 1:2:2 and
2:1:1, respectively (93). Bile, which is of course a secretion of the
liver, contains only one phospholipid, namely, lecithin (94, 95).
Hanahan (14) has reported that the fatty acids of the lysolecithins
produced from the liver lecithins of beef, rabbit, rat, guinea pig, and
dog by the action of lecithinase A of snake venom are all saturated. On
the basis of the specificity of lecithinase A of snake venom for the a'
fatty acid of lecithin (96), this was interpreted to indicate an asymmetric distribution of fatty acid in liver lecithin. A similar asymmetry
has been reported by Borgström (97) and Johnston and Nakayama
(98) for the lecithin of bile. Recently some doubt has been cast on the
specificity of lecithinase A (15, 99), and this will have to be resolved
before the asymmetry of lecithin can be fully resolved. More recently,
Dittmer and Hanahan (100) have determined the fatty acid compositions of the three major phospholipids of rat liver. The data, including
a division of the fatty acids of the lecithin on the basis of the action of
lecithinase A, are given in Table X. It is interesting to note that the
TABLE X
FATTY ACID COMPOSITION OF RAT LIVER PHOSPHOLIPIDS"
Arüchi- Dooosii
-
Phospholipid
Linoleic donic hexaenoic Palmitic Oleic Stearic
Phosphatidylethanolamine
6
10.1
23.6
9.6
20.9
10.6
23.2
Phosphatidylcholine released
by lecithinase A
Lysolecithin
Phosphatidylinositol
α From Dittmer and Hanahan (100). Data reported in molar per cent of total fatty
acid.
b Contains approximately 3% phosphatidylserine.
fatty acids of the phosphatidylinositol of beef liver are reported by
Faure et al. (88) to be a mixture of stearic acid and unsaturated fatty
acids.
E. EGGS
Of animal tissues and products not described above, only eggs have
been thoroughly enough investigated to warrant detailed discussion of
their phospholipids. Most of this work has been done on chicken eggs;
however, a comparative study by Masuda and Hori (101) gives the
lecithin concentration as weight per cent of total phospholipid of an
32.8
<
4.0
41.0
— 4.2—
38.2
10.6
>
9.1
3.7
44.8
7.9
9.3
9.6
5.3
2.4
41.2
37.9
251
Among other phospholipids that have been reported in rat liver but are
not yet well characterized is one containing glutamic acid (92) and two
which have amino nitrogen: phosphorus : fatty acid ratios of 1:2:2 and
2:1:1, respectively (93). Bile, which is of course a secretion of the
liver, contains only one phospholipid, namely, lecithin (94, 95).
Hanahan (14) has reported that the fatty acids of the lysolecithins
produced from the liver lecithins of beef, rabbit, rat, guinea pig, and
dog by the action of lecithinase A of snake venom are all saturated. On
the basis of the specificity of lecithinase A of snake venom for the a'
fatty acid of lecithin (96), this was interpreted to indicate an asymmetric distribution of fatty acid in liver lecithin. A similar asymmetry
has been reported by Borgström (97) and Johnston and Nakayama
(98) for the lecithin of bile. Recently some doubt has been cast on the
specificity of lecithinase A (15, 99), and this will have to be resolved
before the asymmetry of lecithin can be fully resolved. More recently,
Dittmer and Hanahan (100) have determined the fatty acid compositions of the three major phospholipids of rat liver. The data, including
a division of the fatty acids of the lecithin on the basis of the action of
lecithinase A, are given in Table X. It is interesting to note that the
TABLE X
FATTY ACID COMPOSITION OF RAT LIVER PHOSPHOLIPIDS"
Arüchi- Dooosii
-
Phospholipid
Linoleic donic hexaenoic Palmitic Oleic Stearic
Phosphatidylethanolamine
6
10.1
23.6
9.6
20.9
10.6
23.2
Phosphatidylcholine released
by lecithinase A
Lysolecithin
Phosphatidylinositol
α From Dittmer and Hanahan (100). Data reported in molar per cent of total fatty
acid.
b Contains approximately 3% phosphatidylserine.
fatty acids of the phosphatidylinositol of beef liver are reported by
Faure et al. (88) to be a mixture of stearic acid and unsaturated fatty
acids.
E. EGGS
Of animal tissues and products not described above, only eggs have
been thoroughly enough investigated to warrant detailed discussion of
their phospholipids. Most of this work has been done on chicken eggs;
however, a comparative study by Masuda and Hori (101) gives the
lecithin concentration as weight per cent of total phospholipid of an
32.8
<
4.0
41.0
— 4.2—
38.2
10.6
>
9.1
3.7
44.8
7.9
9.3
9.6
5.3
2.4
41.2
37.9