Distribution of phospholipids, fatty acids, and platelet factor 3 activity
among subcellular fractions of human platelets
MJ Broekman, RI Handin, A Derksen and P Cohen
As compared with other methods, our recently reported method for
subcellular fractionation of human platelets improves the separation of
mitochondria, alpha granules, and lysosomal enzyme activities. The relative
purity of these fractions has led us to undertake the present study to
compare the subcellular distribution of phospholipids, fatty acids, and
platelet factor 3 (clot-promoting) activity. Two findings pertaining to
distribution of phospholipids were entirely new. (1) In the alpha granule
zone, plasmalogen phosphatidyl ethanolamine peaked at the expense of diacyl
phosphatidyl ethanolamine. (2) The fatty acid composition of the membrane
lysophosphatidyl choline suggested that it may have been formed by the
action of platelet phospholipase A2 activity. The fatty acids of the
membranes showed a markedly asymmetrical distribution in noncholine versus
choline phospholipids. The latter held 94%, 72%, and 85%, respectively, of
the total content of 16:0, 18:1, and 18:2 fatty acids, whereas 55% of the
18:0, 72% of 20:4, and 67% of higher polyenoic acids other than 20:4 were
esterified to the noncholine group. The most important new information
related to clot-promoting activity, which, on the basis of protein content,
was highest in the membrane fractions, but on the basis of phospholipid
content in the nonmembranous fractions. The discussion centers on possible
explanations for this novel finding.
Volume 47,
Issue 6,
pp. 963-971,
06/01/1976
Copyright © 1976 by The American Society of Hematology
