Synthesis of proteins from [35S]methionine by guinea pig megakaryocytes in
vivo and time course of appearance of newly synthesized proteins in
platelets
BP Schick
Cardeza Foundation for Hematologic Research, Jefferson Medical College,
Thomas Jefferson University, Philadelphia, PA 19107.
The relationship of protein synthesis to megakaryocyte maturation has been
studied in guinea pigs in vivo. Guinea pigs were injected with a single
dose of [35S]methionine. Megakaryocytes and platelets were isolated daily
for 4 days, and proteins from both cells were isolated by DEAE-Sephacel
chromatography and analyzed by sodium dodecyl sulfate- polyacrylamide gel
electrophoresis (SDS-PAGE) and fluorography. All proteins in megakaryocytes
corresponding to stained bands on the SDS- PAGE gels were radiolabeled at 3
hours after injection. The greatest loss of radioactivity from the
megakaryocytes occurred between 1 and 3 days after injection. Only trace
labeling of platelet proteins was seen at 3 hours, representing almost
entirely three bands at molecular weights 47,000, 52,000, and 66,000. At 24
hours only about 13% of the maximal labeling was present, but not all
proteins were labeled. The maximal labeling was at 3 days. The pattern of
labeling of platelets at 3 days was identical to that of megakaryocytes at
3 hours. The protein pattern of nonmegakaryocytic marrow cells was
different from that of the platelets and megakaryocytes. Data presented
here suggest that most protein synthesis in megakaryocytes is completed at
least 24 hours before release of the platelets to the circulation, and
suggest some specificity in the proteins that are synthesized at the
terminal stages of maturation.
Volume 76,
Issue 5,
pp. 887-891,
09/01/1990
Copyright © 1990 by The American Society of Hematology
