Aconitine is one of the most toxic alkaloids, however, the pharmacokinetics is largely unknown mainly due to the difficulty in quantitative analysis of the toxin from biological materials, such as blood and urine. Recently, a Selected Ion Monitoring Method using GC-MS has been applied to the quantitative determination of the toxin by Mizugaki et al. (Eisei Kagaku, 34,359-365,1988). The purpose of this study is to investigate the toxico-kinetics of aconitine by measuring it in the biological specimens. By using the Selected Ion Monitoring Method, we have gotten the satisfactory results of quantitative determination of aconitine from the biological specimens, though we costed almost a year. Moreover, we improved the more accurate analysis of aconitine by using hypaconitine as the internal standard.
Male mice of ICR strain weighing 30-35 g were used for animal experiments. Aconitine (Sigma Chemical Co.) was dissolved in a 0.1 M acetate buffer (pH 5.0), and mice were injected intraperitenea
lly with the toxin at the doses of 0.3 or 0.35 mg/kg (LD_<50> of aconitine for mice is known to be 0.308mg/kg i.p.). The mice were killed by cervical dislocation at 5,15,30,45,60, and 120 min after the administration (n=3, respectively), and blood samples were collected from the heart. At a dose of 0.3 mg/kg of aconitine, the blood concentration reached to the maximum, 17.2 ng/ml, at 15min, and decreased logarithmically to 5.63 ng/ml at 120 min. At a dose of 0.35 mg/kg of aconitine, the blood concentration reached to the maximum, 32.1 ng/ml, at the same time as the 0.3 mg/kg dose, and decreased to 10.7 ng/ml at 120 min. By plotting the blood concentrations of aconitine in logaritmic scale against the time after administration, the linear curves of the blood aconitine elimination were obtained after 30 min at both doses. From the curves the elimination velocity constants (K_<el>s) were calculated to be 0.00718 /min and 0.00835 /min, and the elimination half-time (T_<1/2>s) were to be 96.5 min and 83.0 min at doses of 0.3 mg/kg and 0.35 mg/kg, respectively. In conclusion, we revealed that the elimination velocity of aconitine is proportional to the blood concentration at the both doses.
We previously reported in mice that the time of death at a dose of 0.4 mg/kg of aconitine was delayd by coadministration of tetrodotoxin (0.01 mg/kg), as antagonist of aconitine in the sodium channel in the exitable membranes (Y.OHNO et al., Tohoku J.Exp.Med., 167,155-158,1992). In this study, however, coadministration of tetrodotoxin (0.01 mg/kg) did not delay the time of death at doses of 0.3 mg/kg and 0/35 mg/kg of aconitine. So, on the continueous studies, the interactions of the two toxins in vivo have to be examined with combinations of various doses of the two toxins. Less