Acetyltransferase activity in human platelet microsomes and washed platelets

Area of Science:

• Biochemistry
• Hematology
• Cell Biology

Background:

• Human platelets generate platelet-activating factor (PAF) upon stimulation by agents like thrombin and collagen.
• The precise biochemical pathway for PAF biosynthesis in platelets remains incompletely understood.

Purpose of the Study:

• To investigate the role of acetyltransferase in platelet-activating factor (PAF) formation.
• To elucidate the mechanism underlying PAF biosynthesis in human platelets.

Main Methods:

• Assessing acetyltransferase activity in human platelet microsomes using [3H]acetyl-CoA and lyso-PAF.
• Measuring acetyltransferase activity in whole platelets stimulated with thrombin or ionophore A-23187, using [3H]acetate.
• Detecting radioactive PAF formation under stimulated and unstimulated conditions.

Main Results:

• Stimulation of human platelets with thrombin or ionophore A-23187 significantly increased acetyltransferase activity in microsomes (2-4 fold).
• Acetyltransferase activity was confirmed in whole platelets upon stimulation, leading to the formation of radioactive PAF.
• No PAF was detected in unstimulated platelets, highlighting the role of stimulation in the process.

Conclusions:

• Acetyltransferase activity is elevated in human platelets upon stimulation.
• These findings strongly suggest that acetyltransferase plays a crucial role in the biosynthesis of platelet-activating factor (PAF).