THE INCORPORATION OF RADIOACTIVE PHOSPHORUS INTO THE PHOSPHOLIPIDS OF HUMAN LEUKEMIC LEUKOCYTES AND PLATELETS*

Abstract

The phospholipid composition of platelets and leukocytes was determined after they were isolated by differential centrifugation from the blood of patients with acute and chronic leukemia. In addition, incorporation in vitro and in vivo of Na2Hp32O4 into the phospholipids of platelets and leukocytes was studied. The phospholipids were separated and identified by silicic acid column chromatography, by chromatography utilizing silicic acid-impregnated paper, and by study of the products of acid and alkaline hydrolysis. The phospholipid composition of both platelets and leukocytes was similar and included phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, sphingomyelin, a phosphoinositide, probably phosphatidylinositol, and a component believed to be phosphatidic acid. Platelets and leukocytes of patients given Na2Hp32O4 intravenously for therapy contained labeled phospholipids 18 hours after the p32 was administered. The P32 was found principally in phosphatidylethanolamine, phosphatidylcholine, and the phosphoinositide. Platelets and leukocytes from leukemic patients and platelets from normal subjects incorporated p32 rapidly into all phospholipid components when incubated with Na2Hp32O4 in vitro. The phosphatidic acid and phosphoinositide components contained 6 to 40 times as much radioactivity as did the others. The experiments demonstrate that platelets and leukocytes from patients with leukemia have very active phospholipid metabolism similar to that reported for other cells.