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

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analysed for LH. Rats were necropsied and histology (limited to mammary tissue, uterus, vagina and
ovaries by the study plan) was not reported. Rats showing abnormal E2 data were excluded from the
results.
There were no compound-related effects in mortality or clinical signs. Body weight, bodyweight
gain and food consumption were significantly decreased in rats at the highest dose tested
compared with controls.
The percentage of days in estrus was significantly increased during the 21–22 and 25–26-week
periods at 400 ppm. The percentage of days in estrus was also increased during the 21–22 and 25–26-
week periods at 50 ppm, but the increase was only significant for the 21–22-week period (Table 21).
All the rats evaluated had E2 concentrations that were within the acceptable range to prime the
LH surge in the hour preceding and during the rise of LH. The baseline (11:00) LH values were similar
among groups. In non-repeat bled rats, LH surges comparable to those in controls were observed
at 25 and 50 ppm, while rats at 400 ppm failed to have an LH surge, with LH values never rising
above baseline. In repeat-bled rats, the LH surge was also severely attenuated at 400 ppm and less
so at 50 ppm (maximum increase over baseline was 157% compared with maximum increase over
baseline of of 273% in controls). Prolactin concentrations increased over the course of the sampling
period in all groups, with peak values noted at 14:00 and 16:00, and began to return to their baseline
values by 20:00 biological time. Treatment with atrazine had no effect on prolactin concentrations.
Most of the rats at termination had distended uteri with fluid-filled lumen, a condition commonly
seen in ovarietomized, E2-stimulated rats. Selected tissues were saved for histopathology, but
the absence of the histopathology report was not considered to be of significance when interpreting
the results.
Table 21. Selected findings in a study designed to evaluate the effects of atrazine on the
pre-ovulatory LH surge and on the estrous cycle in rats
Finding
Dietary concentration (ppm)
0 25 50 400
Body-weight gain (g), weeks 1–26 133 138 131 114*
Food consumption (g), weeks 1–25 3438 3462 3455 3309*
Percentage of days in diestrus/estrus
Weeks 1–2 58/22 57/22 56/22 61/21
Weeks 13–14 49/31 53/28 49/31 44/40*
Weeks 17–18 47/34 49/33 47/36 41/45*
Weeks 21–22 51/32 43/41 39**/45* 37**/51**
Weeks 25–26 40/47 42/48 34/54 29*/63*
LH (pg/ml), non-repeat bled rats:
11:00 1900 1816 1581 1863
18:00 3456 3235 3175 1358*
20:00 2327 2249 1899 1308*
LH (pg/ml), repeat-bled rats: 909 1075 972 1005
11:00
18:00 3336 3631 2500 858*
20:00 3388 2510 2409 1042*
From Morseth (1996c)
LH, luteinizing hormone.
* p < 0.05; ** p < 0.01.
ATRAZINE 37–138 JMPR 2007