TY - JOUR
T1 - Utilization of a continuous flow reactor to study the lipoprotein-associated coagulation inhibitor (LACI) that inhibits tissue factor
AU - Gemmell, C. H.
AU - Broze, G. J.
AU - Turitto, V. T.
AU - Nemerson, Y.
PY - 1990
Y1 - 1990
N2 - A microperfusion system containing a glass capillary, the inner surface of which is coated with a phospholipid bilayer containing tissue factor, was used to explore the requirement for factors VIIa and Xa in the complex formed with the lipoprotein-associated coagulation inhibitor (LACI). Various combinations of factors VIIa, Xa, and LACI were perfused together or sequentially at a wall shear rate of 300 sec-1; a final perfusion of factors X and VIIa was performed to evaluate the residual tissue factor activity. Factor Xa concentration at the outlet of the tube was determined using a chromogenic substrate. In the presence of factors VIIa, Xa, and LACI, complete inhibition of tissue factor was observed on both phosphatidylcholine (neutral surfaces) and on phosphatidylserine/phosphatidylcholine (acidic) surfaces; omission of factors Xa or LACI resulted in no inhibition. The absence of factor VIIa in the initial perfusion steps resulted in no inhibition on neutral surfaces whereas about 90% inhibition was observed on acidic surfaces. Initial perfusion with factor Xa, but not LACI, followed by the remaining protein components, resulted in an inhibitory complex. Thus, it appears that a tissue factor:factor Xa:LACI complex can form in the absence of factor VIIa on acidic surfaces; moreover, our data imply a tissue factor binding site for factor Xa, but not for LACI.
AB - A microperfusion system containing a glass capillary, the inner surface of which is coated with a phospholipid bilayer containing tissue factor, was used to explore the requirement for factors VIIa and Xa in the complex formed with the lipoprotein-associated coagulation inhibitor (LACI). Various combinations of factors VIIa, Xa, and LACI were perfused together or sequentially at a wall shear rate of 300 sec-1; a final perfusion of factors X and VIIa was performed to evaluate the residual tissue factor activity. Factor Xa concentration at the outlet of the tube was determined using a chromogenic substrate. In the presence of factors VIIa, Xa, and LACI, complete inhibition of tissue factor was observed on both phosphatidylcholine (neutral surfaces) and on phosphatidylserine/phosphatidylcholine (acidic) surfaces; omission of factors Xa or LACI resulted in no inhibition. The absence of factor VIIa in the initial perfusion steps resulted in no inhibition on neutral surfaces whereas about 90% inhibition was observed on acidic surfaces. Initial perfusion with factor Xa, but not LACI, followed by the remaining protein components, resulted in an inhibitory complex. Thus, it appears that a tissue factor:factor Xa:LACI complex can form in the absence of factor VIIa on acidic surfaces; moreover, our data imply a tissue factor binding site for factor Xa, but not for LACI.
UR - http://www.scopus.com/inward/record.url?scp=0025223140&partnerID=8YFLogxK
U2 - 10.1182/blood.v76.11.2266.2266
DO - 10.1182/blood.v76.11.2266.2266
M3 - Article
C2 - 2257300
AN - SCOPUS:0025223140
VL - 76
SP - 2266
EP - 2271
JO - Blood
JF - Blood
SN - 0006-4971
IS - 11
ER -