Summary
The generation of thrombin was studied in an activating system consisting of purified
thrombin zymogens, purified autoprothrombin C, purified Ac-globulin, lipid or bile
salts, and calcium chloride. With the concentration of calcium ions and pH fixed,
the effect of varying the other three procoagulants was studied. Bile salts were effective
substitutes for lipids in a concentration where micelles form. The approximate effectiveness
from highest to lowest was: conjugated sodium salt of taurocholic acid, sodium cholate,
sodium deoxycholate. Sodium dehydrocholate was ineffective. Autoprothrombin C is the
enzyme for thrombin formation. For accelerating its activity best results were obtained
with the simultaneous presence of optimal concentrations of calcium ions, Ac-globulin
and lipids or bile salts. Reducing any one of the three to zero concentration decreased
the rate and yield of thrombin generation.
The form in which the zymogen is used was found to be important. Prothrombin complex,
DE AE-prothrombin and prethrombin were studied. Each substrate has its peculiar requirements
for yielding thrombin. Prothrombin complex and DEAE-pro-thrombin activated far more
rapidly and required 10 times less autoprothrombin C than prethrombin. The yield of
thrombin from these substrates was also higher than from prethrombin. DE AE-prothrombin
required the least amount of lipid. For the bile salts the required concentrations
were nearly always the same from one substrate to another. To a certain extent Benadryl
could also be substituted for lipids. In association with rapid thrombin generation
from DE AE-prothrombin the Ac-globulin and autoprothrombin C Avere represented in
approximately a 6:1 molar ratio. As compared with the weight of the enzyme large amounts
of Ac-globulin and cholate were required.
DE AE-prothrombin was readily made refractory to the two-stage analytical reagents
with purified platelet factor 3 and calcium ions. Combinations of sodium cholate and
phosphatidyl serine were also effective, but either one alone was ineffective.