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The formation of a platelet adhesive factor by disruption of the creatine phosphokinase molecule
Insights
A novel platelet adhesive factor (PAF) forms from creatine phosphokinase (CPK) enzyme breakdown, causing platelet aggregation. This discovery offers insights into thrombosis and exercise-related conditions.
Area of Science:
- Biochemistry
- Hematology
- Enzymology
Background:
- Platelet aggregation is crucial for hemostasis and thrombosis.
- The precise mechanisms initiating platelet adhesion are not fully understood.
- Creatine phosphokinase (CPK) is an enzyme involved in cellular energy metabolism.
Purpose of the Study:
- To investigate the formation and nature of a platelet adhesive factor (PAF).
- To explore the role of CPK in PAF generation.
- To assess the potential in vivo relevance of PAF in platelet adhesion.
Main Methods:
- In vitro incubation of CPK with glutathione (GSH) or cysteine.
- Enzyme activity assays and heat denaturation of CPK.
- Biochemical and biophysical characterization of PAF (chromatography, electrophoresis, ultracentrifugation).
- In vivo studies in animals involving intravascular PAF administration.
Main Results:
- CPK breakdown products, particularly from heat or chemical inactivation, generated PAF.
- PAF induced in vitro platelet adhesion, with variable responses among individuals.
- PAF formation is linked to the disruption of the CPK dimeric structure.
- Animal studies showed decreased circulating platelets post-PAF administration.
Conclusions:
- PAF, derived from CPK disruption, is a novel initiator of platelet adhesion.
- The findings suggest a biophysical mechanism for platelet aggregation.
- This mechanism may be relevant to physiological processes like exercise and pathological conditions such as thrombosis.
Abstract:
It was discovered that the product of a mix containing the enzyme creatine phosphokinase (CPK) and either glutathione (GSH) or cysteine caused platelets to adhere together in vitro. This platelet adhesive factor (PAF) was formed as CPK enzyme activity declined. An alternative method for the destruction of enzyme activity--heat at 56 degrees C--also resulted in the formation of an in-vitro active PAF which was both less stable and active than its chemically produced counterpart. Assay of the platelet adhesive potency of the CPK-GSH mix, using human platelets, revealed a wide variation in the response of different individuals' platelets to standard quantities of PAF. The nature of this preparation of PAF was investigated by both biochemical and biophysical means, including ion exchange chromatography, electrophoresis, amino acid analysis and analytical ultracentrifuge studies. Evidence is presented that PAF is the product of the disruption of the dimeric structure of the CPK molecule. PAF was found to adhere to paper, under the conditions of electrophoresis imposed, and also to cause sephadex beads to bind together, characteristics which suggested that the platelet adhesion reaction was probably a biophysical process. Red and white cells were not similarly affected. The feasibility of this novel concept for the initiation of platelet adhesion, as a naturally occurring process, was supported by the results of animal experiments in which a statistically depression of platelets in the systemic circulation followed the intravascular administration of PAF. The possible relevance to man of this basic mechanism in relation to exercise and disease processes, including ideopathic and post-traumatic thrombosis, atherogenesis, and dysbaric aseptic necrosis of bone, is discussed.