Summary
A hypothesis is put forward according to which the platelet release reaction and viscous
metamorphosis are connected with platelet lysosome activation. An essential element
of this hypothesis is the assumption of ATPase activation which results in ATP breakdown
and ADP release.
The following findings are described :
1. A variety of agents was studied in regard to their ability to induce the release
reaction. It was found that thrombin, trypsin, papaine, elastase, protease from streptomyces
griseus, connective tissue “extracts”, contact factor preparations, kaolin suspensions
and Triton X-100 induce the release of adenine nucleotides from platelets.
2. All the studied release inducing agents activated to some extend the platelet acid
phosphatase.
3. Streptolysine 0 and staphylocoagulase induce the platelet release reaction as well
as the activation of platelet acid phosphatase.
4. Agents known to labilize liver lysosomes induce some release of adenine nucleotides
from platelets and activate platelet acid phosphatase.
5. Prednisolone succinate which is known to stabilize lysosomes, inhibits the activation
of acid phosphatase provoked by release inducing agents.
6. The activation of liver lysosome acid phosphatase by platelet release inducing
agents was irregular and small.
7. The ATPase activity of thrombosthenin preparations and of dialysed platelets was
found to be increased by thrombin.
8. N-ethylmaleimid inhibits the platelet release reaction while ouabaine did not so.
The proposed hypothesis is discussed in the light of the recent lysosome research.
