Influence of β₂-Glycoprotein-l Upon the Content of cAMP and cGMP in Human Blood Platelets

Summary

The influence of β₂-glycoprotein-I on the cyclic nucleotide content in human gel filtered platelets (GFP) was studied: 1) β₂-G-I up to a concentration of 5 mg/ml does not alter the basal cAMP level in resting GFP and also does not influence the action of PGE₁ which strongly inhibits platelet aggregation by elevation of cAMP.

2) Collagen induced aggregation of GFP leads to an increase of the platelet cGMP content. Preincubation of GFP with 0.2 mg/ml of β₂-G-I enhances significantly the cGMP increase by collagen.

3) In a similar manner β₂-G-I also amplifies the increase in cGMP concentration induced by ADP. In this case, a concomitant alteration of the aggregation pattern is observed.

4) Thrombin produces a much higher cGMP elevation in GFP than ADP or collagen. The admixture of 0.2 mg/ml of β₂-G-I is not able to enhance further the thrombin effect on cGMP. The results are discussed in view of the possible significance of these observations for platelet aggregation in vivo.

Key words

β₂-glycoprotein-I - cAMP - cGMP - Platelet aggregation

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