Mechanism of rabbit platelet agglutination induced by acidic mucopolysaccharide extracted from Stichopus japonicus Selenka.

The effects of acidic mucopolysaccharide extracted from sea cucumber (Stichopus japonicus Selenka) (SJAMP) on rabbit platelets were studied. Using citrated platelet-rich plasma (PRP), washed platelets, and formaldehyde fixed platelets from 10 New Zealand white rabbits, we investigated the effects of platelet inhibitors and various plasma and its fractions on SJAMP-induced agglutination. It was found that the tracing of platelet agglutination induced by SJAMP showed a single phase without a lag period. The lowest concentration of SJAMP required for the agglutination of rabbit platelets was approximately 2 micrograms/ml, and the magnitude of agglutination induced by SJAMP was concentration dependent. In 8 out of 10 rabbits, the platelets in PRP were agglutinated by 10 micrograms/ml of SJAMP. Platelet inhibitors, such as aspirin, indomethacin, apyrase, antimycin, 2-deoxy-D-glucose and EDTA did not inhibit the agglutination induced by SJAMP. Washed rabbit platelets were not agglutinated by SJAMP even though the concentration of SJAMP was raised up to 50 micrograms/ml. When rabbit plasma, serum, or 50-60% ammonium sulfate saturated plasma fraction was added to the reaction mixture, agglutination of washed platelets by SJAMP was recovered completely. But human plasma or fibrinogen did not have any effect on the reactivity of washed rabbit platelets to SJAMP. From these data we conclude that the SJAMP-induced rabbit platelet agglutination is independent of energy metabolism but requires plasma cofactor(s) other than fibrinogen. The plasma cofactor is present in 50-60% ammonium sulfate saturated plasma fraction.