Pesticide residues in food — 2007: Toxicological ... - ipcs inchem

159
reduced motor activity in males and females of the control group noted on day 0 was attributed to
overnight fasting. In males, the motor activity was depressed by about 14% at 12 mg/kg bw relative
to that of the controls, with partial recovery on day 7, and complete recovery of activity was seen
by day 14. In females, motor activity appeared to be slower to recover, showing deficits of about
20%, 10% and 8% at 1, 3 and 6 mg/kg bw, respectively, relative to values for the corresponding
controls on day 14.
Dose-related changes in locomotor activity were also noted in males on day 0, with about
47% and 77% depressions at 6 and 12 mg/kg bw respectively, relative to values for the corresponding
controls. In females, the reductions in locomotor activity were about 26%, 15% and 63% at 1, 3
and 6 mg/kg bw respectively, in comparison to those for the parallel controls. Complete recovery of
locomotor activity was seen in all males and females, except for males at 12 mg/kg bw that showed
a deficit of 20% compared with the controls by day 7. Complete recovery was seen in all animals by
day 14. Treatment-related reductions were also seen in interval motor and locomotor activities on day
0 after treatment, but recovery was complete by day 7. Habituation was not affected by treatment.
Data on cholinesterase activities are shown in Table 15.
No intergroup differences were noted in terminal body weights, brain weight, gross pathology
and histopathology of treated rats of either sex. The NOAEL was 2 mg/kg bw per day on the
basis of a significant reduction in brain cholinesterase activity at higher doses (Sheets & Hamilton,
1994).
In a short-term study of neurotoxicity, groups of 18 male and 18 female Fischer 344 rats
were given diets containing azinphos-methyl (purity, 92.2%) at a nominal dose of 0, 15, 45, or
120 ppm for males (mean intake, 0.91, 2.81, or 7.87 mg/kg bw per day) and 0, 15, 45, or 90 ppm
for females (mean intake, 1.05, 3.23, or 6.99 mg/kg bw per day) for 13 weeks. Twelve of the rats
in each group were used for behavioural testing with half of these being used for neuropathology.
The remaining six males and six females per group were tested for cholinesterase activity. There
were no deaths before terminal sacrifice. Treatment-related clinical signs (perianal stain, red lacrimation,
increased reactivity, uncoordinated gait, tremor) were evident by cage-side observations
Table 15. Cholinesterase activity (relative to the corresponding controls) in rats given
azinphos-methyl by gavage
Dose (mg/kg bw)
Cholinesterase activity (% relative to corresponding controls)
Plasma a Erythrocytes a Brain a
Males
2 32* 33* 15
6 57* 67* 74*
12 b 50* 63* 88*
Females
1 11 17 5
3 36* 65* 51*
6 c — — —
From Sheets & Hamilton (1994)
a
Six males and six females.
b
Four animals died after treatment on day 0.
c
All six animals in the group died after treatment on day 0.
*
Significantly different from the corresponding controls (p ≤ 0.05)
AZINPHOS-METHYL 139–172 JMPR 2007