| Summary: | 碩士 === 國立臺灣大學 === 藥理學研究所 === 82 === By means of ionic exchanger and gel filtration chromatography,
a novel snake venom protein,Agkistin,purified from Agkistrodon
Acutus (hundred-pace snake) specifically inhibited ristocetin-
induced human platelet aggregation.Agkistin was homogenous as
judged by SDS-PAGE.Its apparant molecular weight was estimated
to be 28,700 daltons as measured by SDS-PAGE.Upon reduction,
Agkistin was shown to contain two subunits with molecular
weight of 16,500 and 15,500 daltons,respectively. In human
platelet-rich plasma and platelet suspension,Agkistin
concentration-dependently inhibited ristocetin-induced platelet
aggregation and agglutination.However,Agkistin apparatently did
not affect platelet aggregation induced by collagen,U46619 and
ADP.Agkistin did not inhibit thrombin-induced platelet aggrega-
tion of human platelet suspension.However,it concentration-de-
pendently inhibited thromboxane A2 formation and prolonged the
latent period in triggering aggregation by low dose of
thrombin. In platelet binding study,125I-Agkistin specifically
bound to unactivated platelets in a saturable manner.The number
of binding sites was estimated to be 61183±3649 per platelet
and the Kd values were estimated to be 2.23±0.11x10-7M.This
binding reac- tion is rapid and reversible.Monoclonal
antibodies,AP1 and 6D1 raised against platelet GPIb blocked
125I-Agkistin binding to platelets.However,monoclonal antibody,7
E3,raised against GP IIb- IIIa complex and snake venom peptide
trigramin,ADP and EDTA did not affect 125I-Agkistin binding
reaction.In vivo study,Agkistin significantly prolonged the
bleeding time of mice when given in- travenously.Therefore,
Agkistin may be utilized as a research tool to develop a new
class of antithrombotic drugs through the struc- ture-activity
relationship study,and to elucidate the role of GP Ib in the
activating process of platelets by thrombin.
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