Placental anticoagulant protein-I: measurement in extracellular fluids and cells of the hemostatic system.
Placental anticoagulant protein-I (PAP-I), a member of the lipocortin protein family, is a potent in vitro anticoagulant whose in vivo function is unknown. Very low levels of PAP-I were present in plasma of normal volunteers (0 to 5 ng/ml) and in randomly chosen plasma specimens from hospitalized patients (0 to 28 ng/ml). Review of selected hospital records did not reveal any single clinical entity that correlated with plasma levels. PAP-I was also found in amniotic fluid (12 to 107 ng/ml) and in conditioned medium of cultured endothelial cells (49 +/- 20 ng/ml). Gel filtration experiments showed that PAP-I was intact and uncomplexed in plasma and amniotic fluid. The protein was fairly abundant intracellularly: 4080 +/- 2560 ng/mg total protein in cultured umbilical vein endothelial cells; 178 +/- 109 ng/mg in platelets; 564 +/- 384 ng/mg in leukocytes; and 8.4 +/- 4.3 ng/mg in erythrocytes. The levels of PAP-I increased in platelet-rich plasma after stimulation of platelets with arachidonic acid but not after stimulation with ADP, epinephrine, thrombin, ristocetin, or collagen. These data suggest that PAP-I probably does not function as a circulating natural anticoagulant in normal persons.
Flaherty
M J
MJ
Department of Laboratory Medicine, University of Washington, Seattle.
West
S
S
Heimark
R L
RL
Fujikawa
K
K
Tait
J F
JF
D000653:Amniotic Fluid / Q000032:analysis; D017302:Annexins; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology; D001792:Blood Platelets / Q000032:analysis / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D004912:Erythrocytes / Q000032:analysis; D005110:Extracellular Space / Q000032:analysis*; D005260:Female; D006487:Hemostasis / Q000502:physiology*; D006801:Humans; D007962:Leukocytes / Q000032:analysis; D008970:Molecular Weight; D010974:Platelet Aggregation; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000032:analysis* / Q000097:blood; D012016:Reference Values; D014471:Umbilical Veins
D017302:Annexins; D001095:Arachidonic Acids; D011257:Pregnancy Proteins; D016718:Arachidonic Acid