The Requirement for Viable Platelets in the Coagulation of Heparinized Blood
type: CreativeWork
description: Activated coagulation times (ACT's) of heparinized blood or plasma samples containing normal platelets were compared with ACT’s of heparinized samples containing non-viable or abnormally functional platelets. The non-viable platelets were prepared by freeze/thawing, and the abnormally functional platelets resulted from the addition of adenosine or adenosine 5'-diphosphate (ADP). The ACT’s of the heparinized samples containing treated platelets were considerably longer than the ACT’s performed on samples with untreated platelets. Treated platelets had no effect on unheparinized samples, however. This would indicate that, although platelet factor 3 (PF3) is sufficient to promote clotting of unheparinized blood, viable platelets, in addition, are required for clotting of heparinized blood. A possible hypothesis which explains these findings is as follows: In the unheparinized situation, coagulation factors are activated as clotting takes place. PF3 serves as a surface catalyst, thrombin is generated, and a fibrin clot is formed. The form in which PF3 is available is incidental to clot formation. When heparin is present, however, thrombin is neutralized as fast as it is formed. Quantities sufficient to induce fibrin formation cannot therefore form in the free plasma, and prolonged or infinite clotting times result. In order for coagulation to go to completion, an environment favorable to thrombin generation must be provided. It is probable that, even in heparinized samples, the foreign surface present and the thrombin formed are sufficient to promote platelet aggregation, even though the thrombin levels are too low to directly affect the coagulation system. The interstices of the platelet aggregates provide an environment favorable to thrombin formation. As the platelets aggregate, plasma containing activated clotting factors and heparin is trapped within the platelet clump. Platelet factor 4 (PF4) is released from the platelets and, in the static environment within the…
abstract: Activated coagulation times (ACT's) of heparinized blood or plasma samples containing normal platelets were compared with ACT’s of heparinized samples containing non-viable or abnormally functional platelets. The non-viable platelets were prepared by freeze/thawing, and the abnormally functional platelets resulted from the addition of adenosine or adenosine 5'-diphosphate (ADP). The ACT’s of the heparinized samples containing treated platelets were considerably longer than the ACT’s performed on samples with untreated platelets. Treated platelets had no effect on unheparinized samples, however. This would indicate that, although platelet factor 3 (PF3) is sufficient to promote clotting of unheparinized blood, viable platelets, in addition, are required for clotting of heparinized blood. A possible hypothesis which explains these findings is as follows: In the unheparinized situation, coagulation factors are activated as clotting takes place. PF3 serves as a surface catalyst, thrombin is generated, and a fibrin clot is formed. The form in which PF3 is available is incidental to clot formation. When heparin is present, however, thrombin is neutralized as fast as it is formed. Quantities sufficient to induce fibrin formation cannot therefore form in the free plasma, and prolonged or infinite clotting times result. In order for coagulation to go to completion, an environment favorable to thrombin generation must be provided. It is probable that, even in heparinized samples, the foreign surface present and the thrombin formed are sufficient to promote platelet aggregation, even though the thrombin levels are too low to directly affect the coagulation system. The interstices of the platelet aggregates provide an environment favorable to thrombin formation. As the platelets aggregate, plasma containing activated clotting factors and heparin is trapped within the platelet clump. Platelet factor 4 (PF4) is released from the platelets and, in the static environment within the…
author: Hay, Karen L.
language: English
keywords: Health Information Technology, Blood Coagulation Factors; Blood Platelets.
date published: 1975-08-01T07:00:00Z
date modified: 2026-07-24T02:53:44Z
provider: Loma Linda University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Loma Linda University