|Abstract or Summary
- Although much information is available on lipids in serum and
red cells, only limited data have been reported for white cells and
platelets. In a recent investigation in this laboratory, the concentrations
of cholesterol in the several blood fractions were compared.
The high amounts of cholesterol found in white cell-platelet samples
together with the wide variability in the proportions of free cholesterol
stimulated an interest to study in more detail the lipid composition
of the four blood fractions.
The concentrations of total lipids, the distributions of lipid
classes, and the fatty acid compositions of cholesterol esters, triglycerides,
and phospholipids were determined in serum, red cells,
white cells, and platelets isolated from venous blood obtained from
sixteen adult men and women. Supplementary analyses were made
on nine samples of blood from one person at intervals over a four-week
Modifications of a published method made possible the simultaneous separation of each of the formed elements; serum was
obtained in the usual manner. Satisfactory procedures for total
lipid extraction from each blood fraction were developed by selective
combinations of individual steps of the classical ethanol-diethyl ether
and chloroform-methanol methods. The proportional distribution of
lipid classes in each blood fraction was quantitated by chemical analyses
of cholesterol and lipid phosphorus and subsequent calculations.
Lipid classes were isolated by preparative thin-layer chromatography.
Methyl esters of the major classes were prepared by direct interesterification
and analyzed by gas-liquid chromatography.
Concentrations of total lipid in sera and red cells were similar,
averaging 603 and 555 mg per 100 ml, respectively. White
cells and platelets contained two to three times as much, averaging
3051 and 2587 mg per 100 gm, respectively. The different blood
fractions exhibited characteristic distributions of lipid classes.
Serum was characterized by high cholesterol esters and triglycerides,
together with phospholipids. All cellular components contained
higher proportions of phospholipids and free cholesterol than
serum. White cells and platelets contained higher amounts of cholesterol
esters and free fatty acids than red cells. The fatty acid
compositions of cholesterol esters, triglycerides, and phospholipids
were not constant among the different blood fractions. The proportions
of fatty acids in triglycerides were most similar. Greatest variations in proportions of fatty acids occurred in cholesterol esters.
Lipid classes in all cellular fractions were characterized by containing
significant amounts of unidentified longer chain fatty acids which
were essentially absent in serum.
Individual-to-individual variations among the sixteen subjects
were greater than day-to-day variations of the one subject for total
lipids in serum and red cells, all lipid classes in serum, and phospholipids
in all blood fractions.
The concentrations of lipid in blood fractions showed no relationship
to the age or sex of the subjects or to their assessed intakes
of fat. Fat intakes were quite similar, however.
Differences in the distribution of lipid classes and fatty acid
composition of lipid classes among the four blood fractions for these
healthy subjects suggest the desirability of concurrent analyses of
all blood fractions in studies of lipid metabolism in humans.