Takako Yamaguchi

Rubber additives inhibit the calcium ionophore and thrombin induced activation of rabbit platelets

Abstract Together with the mutagenic activities of 5 rubber vulcanization activators (tetramethylthiuram disulfide[TMTD], zinc dimethyldithiocarbamate[ZDMC], zinc diethyldithiocarbamate[ZDEC], sodium dimethyldithiocarbamate[SDMC] and sodium diethyldithiocarbamate[SDEC]), the effect of these compounds on thrombin or calcium ionophore A-23187 induced activation of washed rabbit platelets has been examined. The mutagenicity was investigated in Ames test, and platelet activation was measured by thromboxane B 2 (TXB 2 ) synthesis and the amount of TXB 2 was determined by enzyme immunoassay (EIA). In mutagenic assay, TMTD, ZDMC and SDMC were mutagenic, on the other hand, all tested compounds inhibited the platelet activation induced by thrombin or A-23187 when they were added simultaneously. The thrombin induced platelet activation was inhibited in proportion to the increased concentration of rubber vulcanization activators. There was not so much IC 50 differences (2–4×10 −8 M) between these compounds against the platelet activation by thrombin. For A-23187 induced platelet activation, the extent of inhibition by these compounds occurred independently of the concentrations used. When platelets were pretreated with these compounds for 5 min before stimulation with thrombin or A-23187, the decreased synthesis of TXB 2 was observed with all compounds. These inhibitory effects were not abolished after removal of the compounds. No correlations were observed between mutagenic activity and inhibitory effect of these rubber vulcanization activators.

Food additives on acceptable daily intake (ADI) level affect the agonist induced platelet activation I. Antioxidants and preservatives

The effect of food additives on cellular functions was examined. Rabbit washed platelets were treated with five antioxidants [butylated hydroxytoluene(BHT), butylated hydroxyanisole(BHA), propyl gallate(PG), ascorbyl palmitate(AP), dl- α -tocopherol(VE)] and three preservatives [thiabendazole(TBZ), diphenyl(DP), o-hydroxydiphenyl(OPP)], and the amount of thromboxane B2(TXB2) synthesized was determined as an indicator of platelet activation. Calcium ionophore A-23187 induced TXB2 synthesis was inhibited by the presence of BHA or PG at 10−6M, BHT or AP at 10−5M. In contrast, thrombin induced TXB2 synthesis was inhibited more significantly than A-23187 induced ones at 10−8M of BHT, PG, AP or VE, 10−7M of BHT. The inhibitory effects of these food additives on A-23187 induced TXB2 synthesis recovered the removal of these compounds, but no recovery was observed in thrombin induced ones. Collagen induced TXB2 synthesis was inhibited by 10−6M levels of BHA or PG, and 10−5M of DP or OPP. AP seemed to have biphasic effects depended on its concentration, and others had no effect on collagen induced TXB2 synthesis.

Effect of halocarbons and styrene on thrombin and calcium ionophore induced activation of rabbit platelets

Abstract The series of study about the effect of environmental pollutants on cell functions, the influence of several volatile halocarbons (trichloroethylene, tetrachloroethylene, trichloroethanol, bromodichlomethane, chlorodibromomethane and bromoform) and styrene on calcium ionophore (A-23187) or thrombin induced activation of washed rabbit platelets has been examined. Platelet activation was measured by thromboxane B 2 synthesis. As a result, tetrachloroethylene and trichloethanol inhibited both A-23187 and thrombin induced platelet activation significantly. Bromoform had an inhibitory action at its highest concentration(10uM) against A-23187 induced platelet activation. Styrene and bromoform revealed a strong inhibitory action against thrombin induced platelet activation. There seemed to be no concentration dependent inhibition of these compounds against platelet activation induced by both agonists. When platelet was pretreated with these compounds, all compounds except trichloroethylene inhibited thrombin induced platelet activation. These result suggest the importance of monitoring the environmental concentration and distribution of widely used volatile compounds which may be potentially hazardous to our health.