Summary
Collagen mediated platelet aggregation caused -5.6 ± 6.7% inhibition and +39.1 ± 15.2%
potentiation of prekallikrein activation in plasma from normal healthy volunteers
between 20–40 and 50–65 years of age, respectively (n = 15, p <0.01). The amouns of
platelet factor-four (PF4) released in the two groups were not significantly different.
Collagen treatment in the presence of indomethacin caused +11.5 ± 3.6% and +59.6 ±
19.5% potentiation in the 20–40 and 50–65 age groups respectively (p <0.02). Adrenaline
mediated platelet aggregation caused -55.2 ± 7.1% and -35.2 ± 8.3% inhibition in the
20–40 and 50–65 age groups, respectively. Collagen treatment of platelet-deficient-plasma
and platelet-rich-plasma in EDTA also caused potentiation of prekallikrein activation.
The results indicate that the observed degree of prekallikrein activation after platelet
aggregation is a net result of the inhibitory effect of PF4 and the potentiatory effect
of activated platelets. The potentiatory effect was greater after collagen treatment
as compared to adrenaline treatment, and in the 50–65 age group as compared to the
20–40 age group.
Key Words
Collagen - Platelets - Prekallikrein - Platelet factor 4
