Cytoskeleton-dependent release of human platelet epidermal growth factor.
To study the source of immunoreactive epidermal growth factor (ir-EGF) released by thrombin formation we removed 99.9% of the leukocytes normally present in platelet-rich plasma and induced coagulation with 30 mM of Ca2+. The absence of leukocytes did not reduce the amount of ir-EGF released; thus platelets are most likely the only source of the ir-EGF released during aggregation. To identify the site of ir-EGF in platelets we exposed washed platelets to collagen or thrombin and compared the kinetics of releases of ir-EGF, beta-thromboglobulin (bTG, an alfa-granule marker), ATP (dense granule marker), N-acetyl-beta-D-glucosaminidase (NAGA, a lysosome marker) and lactate dehydrogenase (LDH, a cytoplasmic marker). Release of ir-EGF started immediately and continued linearly. The process differed clearly from the releases of the granule markers, which occurred readily, and were completed in a few minutes. The release of ir-EGF also differed from the leakage of LDH, the start of which was delayed greater than 5 min, but then proceeded linearly. Cytochalasin B inhibited the release of hEGF, but demecolcine had no effect. We conclude that the ir-EGF released from platelets during aggregation derives neither from the granules nor the cytoplasma. The assembly of cytoskeleton is needed for its release.
Kiuru
J
J
Finnish Red Cross Blood Transfusion Center, Helsinki.
Viinikka
L
L
Myllylä
G
G
Pesonen
K
K
Perheentupa
J
J
D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D003094:Collagen / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D003703:Demecolcine / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000097:blood*; D006801:Humans; D007700:Kinetics; D010974:Platelet Aggregation / Q000502:physiology*; D013917:Thrombin / Q000494:pharmacology
D003571:Cytochalasin B; D004815:Epidermal Growth Factor; D003094:Collagen; D013917:Thrombin; D002118:Calcium; D003703:Demecolcine