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JOHN C. DITTMER
that in human and pig red cells the ratio of phosphatidylcholine to
sphingomyelin is 1.5:1, but that no phosphatidylcholine can be detected
in the red cells of beef. They have also demonstrated the presence of
phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol
in the red cells of all three of these species. No plasmalogen was detected. Dawson and Lindsay (78) have carried out analyses of the
phospholipids of the erythrocyte ghosts of three ruminants and three
nonruminants (Table IX). The different distribution of phospholipids in
ruminant and nonruminant red cells is also found in the ghosts. This
more detailed analysis also reveals that besides the significantly higher
sphingomyelin and lower phosphatidylcholine content in ruminant
erythrocytes, there is also a lower phosphatidylethanolamine content in
the red cells of ruminants and of the horse. It is suggested that this may
be characteristic of the herbivores. The data of Burt and Rossiter (81)
for the erythrocytes of rabbits and of Formijne et al. (82) and Hack
(73) for human red cells are also in line with the findings reported
above.
Turner (83) has suggested that the failure of snake venom to cause
lysis of red cells of ruminants is related to the absence of lecithin;
however, there is still no satisfactory explanation of why the red cells of
the camel should be resistant to lysis by snake venom yet contain
lecithin.
D. LIVER
No comparative study of the distribution of liver phospholipids in
different species has been made, and characterization of the individual
phospholipids of liver is limited to a few mammals, in particular ox
and rat (84, 85). For an organ with as diverse activities as the liver,
the range of phospholipids is quite simple. A little over 50% of the
phospholipid is phosphatidylcholine. Phosphatidylethanolamine (84, 86)
and smaller amounts of phosphatidylserine and phosphatidylinositol (85,
87, 88) and sphingomyelin (84) are present. At least in rat and sheep
liver, plasmalogens are present in only trace amounts (77, 89). Other
phospholipids present in relatively small amounts are phosphatidic acid
(90) and polyglycerophosphatides similar to cardiolipin of heart. This
has been isolated from dog liver by McKibbin and Taylor (91), rat
liver by Dawson (87), and beef liver by Faure et al. (88). The compounds from dog and rat liver have a glycerol: fatty acid: phosphorus
ratio of 3:2:3, and that from beef has a ratio of 3:4:2. Whether this
represents a true species difference has not been resolved. The distributions of these phospholipids in liver of rat and sheep are tabulated
with other organs at the end of the section on animal phospholipids.
JOHN C. DITTMER
that in human and pig red cells the ratio of phosphatidylcholine to
sphingomyelin is 1.5:1, but that no phosphatidylcholine can be detected
in the red cells of beef. They have also demonstrated the presence of
phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol
in the red cells of all three of these species. No plasmalogen was detected. Dawson and Lindsay (78) have carried out analyses of the
phospholipids of the erythrocyte ghosts of three ruminants and three
nonruminants (Table IX). The different distribution of phospholipids in
ruminant and nonruminant red cells is also found in the ghosts. This
more detailed analysis also reveals that besides the significantly higher
sphingomyelin and lower phosphatidylcholine content in ruminant
erythrocytes, there is also a lower phosphatidylethanolamine content in
the red cells of ruminants and of the horse. It is suggested that this may
be characteristic of the herbivores. The data of Burt and Rossiter (81)
for the erythrocytes of rabbits and of Formijne et al. (82) and Hack
(73) for human red cells are also in line with the findings reported
above.
Turner (83) has suggested that the failure of snake venom to cause
lysis of red cells of ruminants is related to the absence of lecithin;
however, there is still no satisfactory explanation of why the red cells of
the camel should be resistant to lysis by snake venom yet contain
lecithin.
D. LIVER
No comparative study of the distribution of liver phospholipids in
different species has been made, and characterization of the individual
phospholipids of liver is limited to a few mammals, in particular ox
and rat (84, 85). For an organ with as diverse activities as the liver,
the range of phospholipids is quite simple. A little over 50% of the
phospholipid is phosphatidylcholine. Phosphatidylethanolamine (84, 86)
and smaller amounts of phosphatidylserine and phosphatidylinositol (85,
87, 88) and sphingomyelin (84) are present. At least in rat and sheep
liver, plasmalogens are present in only trace amounts (77, 89). Other
phospholipids present in relatively small amounts are phosphatidic acid
(90) and polyglycerophosphatides similar to cardiolipin of heart. This
has been isolated from dog liver by McKibbin and Taylor (91), rat
liver by Dawson (87), and beef liver by Faure et al. (88). The compounds from dog and rat liver have a glycerol: fatty acid: phosphorus
ratio of 3:2:3, and that from beef has a ratio of 3:4:2. Whether this
represents a true species difference has not been resolved. The distributions of these phospholipids in liver of rat and sheep are tabulated
with other organs at the end of the section on animal phospholipids.