抄録
In order to make clear the toxicity of two kinds white gasoline containing tetraethyl lead (LG) and organic solvents besides tetraethyl lead (LBTX), the survival rate and the electrocorticogram (E.Co.G.) in rats injected with either of them intraperitoneally were analysed.
Thirtynine white male Wistar rats, weighing about 400 g and aged 7 months, were implanted with bipolar electrodes on the surface of the brain about 3 mm apart over the frontal and occipital lobes of the left hemisphere under Nembutal-ether anaesthesia. The rats were divided into two groups, each rat in one of them was intraabdominally injected with 1 ml/100 g of LG and each rat in the other with the same dosis of LBTX. Tetraethyl lead content of LG was 1. 0 ml/liter that is, 16.5 mg/kg body weight of rat, and LBTX contained 5% benzene, 10% toluene and 15% xylene and 70% LG, tetraethyl lead in LBTX becoming 11.6 mg/kg body weight of rat. RG and HG, used in the former experiment, are commercially available leaded regular and high-octane gasolines. Tetraethyl lead contents of RG and HG were 0.15 ml/liter and 1.41 ml/liter, i.e. the amount of tetraethyl lead in rat were 2.5 mg and 23.3 mg/kg body weight respectively.
Observations were made one month after recovery from the implant operation. Brain waves were recorded on one day before and at 1, 2, 3, 4, 5, 7 and 10 days after the injection. The original wave, the momentary waves of δ, θ, α, β1 and β2 in the E.Co.G. and each 10 second integral value of these brain waves were recorded at the same time, and the data for 5 to 10 minutes were analysed.
One to 4 days after the gasoline injection rats showed slowing of movements, a crouching posture and absence of reaction to stimuli. After fifth day from the gasoline injection, the rats in the LG group showed excessive tension, excitement and anxiety, and the rats in the LBTX group showed continuously the same symptoms as crouching posture and slowing of movements. But about half of the rats in the LBTX group showed delirium and were dead within 2 days after LBTX injection, while almost of the rats in the LG group were alive. The death rate of HG and LG group was similar with LBTX group.
The control E.Co.G. before the injection showed a dominant θ and marked α waves, and the amplitude of these waves ranged from 50 to 150 microvolts. One to 5 days after the gasoline injection the basic rhythm and the amplitude in the E.Co.G. decreased and this phenomenon was more marked in the LBTX group than in the LG group, that is, α wave on the 1st day, δ and β2 waves on the 4th day and θ wave on the 5th day after the gasoline injection decreased significantly compared to those of the LG group. The α wave of the rats in the LG group increased markedly and dominantly 7 days after the LG injection. The E.Co.G. of rats in the serious state before death caused by LBTX showed high voltage fast waves, arhythmic pattern of the brain waves appearing and disappearing, and slow and fast brain waves.
From these results it was concluded that the toxicity of LBTX was stronger than that of LG.
