Groups of 10 male and 10 female Hoe:NMRKf mice were fed diets
containing endosulfan at a concentration of 0 or 18 ppm for six weeks,
equal to 0 or 3.7 mg/kg bw per day for males and 0 or 4.6 mg/kg bw per
day for females, to determine whether 18 ppm was the NOAEL in this
strain, as it was found to be in CD-1 mice in a three-month study
(Barnard et al., 1984). There were no clinical signs attributable to
treatment. The mean food intake of mice receiving endosulfan was
slightly decreased in males and slightly increased in females. Mean
body-weight gain was reduced in treated males during the second half
of the experiment but was slightly increased in females throughout the
experiment. Two treated females died, on days 28 and 38; the causes
were not established, but no histological changes were found in the
mouse that was not autolysed. The absolute and relative weights of the
liver of males and females at 18 ppm were higher than those of
controls and statistically significantly so in females (17 and 12%,
respectively). A NOAEL was not identified, as an increase in liver
weights was seen in females at the only dose tested (Donaubauer et
al., 1985).