Platelet aggregation caused by a partially purified jellyfish toxin from Carybdea rastonii.
A partially purified toxin (pCrTX) was obtained from the tentacles of the jellyfish, Carybdea rastonii. When pCrTX (3 X 10(-8) - 3 X 10(-7) g/ml) was added to citrated platelet-rich plasma, aggregation was produced in a concentration-dependent manner. Scanning electron microscopic examination revealed that both pCrTX and collagen produced aggregates of platelets possessing many pseudopods. The concentration which produced 50% aggregation for pCrTX was 1.8 X 10(-7) g/ml, as compared to 2.3 X 10(-6) g/ml for collagen. The pCrTX-induced aggregation was only slightly inhibited by indomethacin and quinacrine in concentrations sufficient to inhibit arachidonic acid- and collagen-induced aggregation. pCrTX was less active in washed platelets suspended in Ca2+ free medium, whereas the pCrTX-induced aggregation was significantly augmented in the presence of Ca2+. The augmentation of aggregation by Ca2+ was only slightly attenuated by pretreatment with 100 microM verapamil. pCrTX significantly increased the concentration of cytoplasmic free Ca2+ ([Ca2+]i) and depolarized the platelet membrane in concentrations that produced aggregation. The increase in [Ca2+]i caused by pCrTX was little affected by verapamil. The depolarization by pCrTX was unchanged in the presence or absence of Ca2+, or by sodium or potassium transport inhibitors. The movement of 22Na+ into platelets was significantly increased by pCrTX. This increase in the movement of 22N+ into platelets was unaffected by tetrodotoxin. On the other hand, pCrTX-induced aggregation, depolarization and the increase in [Ca2+]i were all significantly attenuated in low Na+ medium. These results suggest that pCrTX causes a massive depolarization by increasing cation permeability indiscriminately and this generalized depolarization permits an inward movement of calcium down an electrochemical gradient which, in turn triggers platelet aggregation.
Azuma
H
H
Sekizaki
S
S
Satoh
A
A
Nakajima
T
T
Ishikawa
M
M
D000818:Animals; D001792:Blood Platelets / Q000378:metabolism / Q000648:ultrastructure; D002118:Calcium / Q000097:blood; D003064:Cnidarian Venoms / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000494:pharmacology*; D003094:Collagen / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D010974:Platelet Aggregation / Q000187:drug effects*; D011817:Rabbits; D037401:Scyphozoa
D003064:Cnidarian Venoms; D003094:Collagen; D002118:Calcium