prothrombin

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prothrombin

 [pro-throm´bin]
a glycoprotein present in the plasma that is converted into thrombin by extrinsic thromboplastin during the second stage of blood clotting; called also factor II.
prothrombin consumption a clinical laboratory test done to determine thromboplastin generating capacity, which provides information about the first stage of blood clotting. When clotting of a normal blood sample occurs, prothrombin is converted to thrombin; thus there should be little or no prothrombin in the serum after the clot is formed. If, however, there is deficiency of blood clotting (coagulation), some of the prothrombin will not be utilized (consumed). Abnormal results of the test are found in deficiencies of the first-stage coagulation factors (factors VIII and IX), and in the presence of circulating anticoagulants, thrombocytopenia, and any other condition leading to inadequate generation of thromboplastin.
prothrombin consumption test a test to measure the formation of intrinsic thromboplastin by determining the residual serum prothrombin after blood clotting is complete.
prothrombin time a test to measure the activity of coagulation factors I, II, V, VII, and X, which participate in the extrinsic pathway of coagulation; abbreviated Pro time or PT. Called also one-stage prothrombin time and Quick's test. Deficiency of any of these factors leads to a prolongation of the one-stage prothrombin times, as will circulating anticoagulants that are active against factors V and VII or against thromboplastin.

The test is considered basic to any study of the clotting process and is also widely used for guidance in establishing and maintaining anticoagulant therapy. Test results are best understood when both the patient's and the control times are reported. The therapeutic range for coagulation therapy is usually 2 to 3 times that of the normal (12 to 15 sec.) control.

pro·throm·bin

(prō-throm'bin),
A glycoprotein, molecular weight approximately 72,500, formed and stored in the parenchymal cells of the liver and present in blood in a concentration of approximately 20 mg/100 mL. In the presence of thromboplastin and calcium ion, prothrombin is converted to thrombin, which in turn converts fibrinogen to fibrin, this process resulting in coagulation of blood; a deficiency of prothrombin leads to impaired blood coagulation.

prothrombin

(prō-thrŏm′bĭn)
n.
A plasma protein that is converted into thrombin during blood clotting.

pro·throm·bin

(prō-throm'bin)
A glycoprotein formed and stored in the parenchymal cells of the liver and present in blood in a concentration of approximately 20 mg/100 mL. In the presence of thromboplastin and calcium ion, prothrombin is converted to thrombin, which in turn converts fibrinogen to fibrin, resulting in coagulation of blood; a deficiency of prothrombin leads to impaired blood coagulation.

prothrombin

A soluble protein in the blood that is converted to the insoluble form thrombin, under the action of the enzyme prothrombinase, at the end of the cascade of events involved in blood clotting. Thrombin is the main ingredient of the blood clot.

prothrombin

see BLOOD CLOTTING.

Prothrombin

Prothrombin is a blood-clotting protein. Injury to a blood vessel produces a signal which triggers the conversion of prothrombin to thrombin. Thrombin is a protein which plays a central role in provoking the assembly of other proteins to form the blood clot.

pro·throm·bin

(prō-throm'bin)
A glycoprotein, formed and stored in the parenchymal cells of the liver and present in blood in a concentration of approximately 20 mg/100 mL; deficiency leads to impaired blood coagulation.