Akiko Hijikata

Potent inhibition of thrombin by the newly synthesized arginine derivative No. 805. The importance of stereo-structure of its hydrophobic carboxamide portion

Abstract Four stereoisomers of 4-methyl-1-[N 2 -(3-methyl-1,2,3,4-tetrahydro-8-quinolinesulfonyl)-L-arginyl]-2-piperidinecarboxylic acid were synthesized and examined for the inhibitory effect on thrombin. The inhibitory potency varied largely with the stereo-configuration of the 4-methyl-2-piperidinecarboxylic acid portion. The (2R, 4R)-isomer was the most potent inhibitor with a Ki of 0.019 μM, while the (2R, 4S) and (2S, 4R)-isomers showed the values of Ki 0.24 and 1.9 μM, respectively. The least potent inhibitor, (2S, 4S)-isomer, showed a Ki of 280 μM which is approximately 15,000 times that of (2R, 4R)-isomer.

Effect of proteases on plasminogen activator release from isolated perfused dog leg

Abstract Inducement of secondary fibrinolysis can be explained most simply by assuming that a substance newly formed in the process of blood coagulation acts on the endothelial cells and releases plasminogen activator (P. A. ) into the circulatory blood. In the present study, it was found that thrombin caused release of P.A. from isolated dog leg perfused with physiological solution. Following administration of purified thrombin to the isolated perfused dog leg, P.A. was released within 10 sec and reached its peak activity at 15∼30 sec. A dose response in P.A. activity released to thrombin was also detected to some extent (1 unit/ml∼50 units/ml). These results suggest that thrombin mediates secondary fibrinolysis. The effects on P.A. release of DFP-treated thrombin and TLCK-treated thrombin, which are inactive in fibrinogen-fibrin conversion, were examined. These chemically modified forms of thrombin did not release P.A. Furthermore, examination of the effects of acetylated thrombin revealed that it also did not cause P.A. release. These results indicate that P.A. is released from the vascular wall by thrombin so long as the latter maintains an intact active center of proteolysis.

A new series of synthetic thrombin-inhibitors (OM-inhibitors) having extremely potent and selective action.

Abstract The studies in searching for potent and highly selective synthetic inhibitors to thrombin led the authors to find a new series of the thrombin-inhibitors which belong to N α -naphthalenesulfonyl-L-arginine derivatives; values of I 50 of these potent inhibitors are found in the range from 0.03 μM to 2 μM, when fibrinogen (3 μM) or N α -benzoyl-L-phenylalanyl-L-valyl-L-arginine p-nitroanilide (100 μM) is used as substrate. These potent thrombin-inhibitors are tentatively called OM-inhibitors according to their code name in our laboratories.

In vitro and in vivo studies of a new series of synthetic thrombin-inhibitors (OM-inhibitors)

Abstract To evaluate the thrombin-inhibitors (OM-inhibitors) synthetized by the authors, their actions in vitro and in vivo have been investigated. Results obtained are summarized as follows: 1. (i) The inhibitory action of the OM-inhibitor (OM-205) is highly selective to thrombin when compared with trypsin, plasmin or reptilase. 2. (ii) The mode of inhibition of the OM-inhibitor (OM-46) to thrombin is competitive in the hydrolysis of Nα-benzoyl-DL-arginine p-nitroanilide. 3. (iii) The decreasing effects of thrombin infusion in rabbits on plasma fibrinogen content and platelets in number are remarkably blocked by the presence of the OM-inhibitor (OM-189) in the blood, which suggests that the OM-inhibitors, very effective in vitro, possess the anti-thrombin activity also in vivo.

Some properties of the tissue plasminogen activator from the pig heart.

Abstract A purified preparation of tissue plasminogen activator was obtained from acetone-dried pig heart powder, principally based on the methods described by Bachmann et al. (1) and Rickli & Zaugg (2). The preparation exhibited the following properties; (i) the molecular weight similar to egg albumin, (ii) the relative thermal stability at neutral pH, (iii) inhibition by EACA and t-AMCHA, (iv) inhibition by DFP and (v) stability to iodoacetamide and TLCK. An additional study indicated that the tissue plasminogen activator was well adsorbed to polyacrylonitrile fiber and eluted with aqueous ammonia.