III. RESULTS: MICE 



THIRTEEN-WEEK STUDIES 



Two of 10 male mice that received 5,000 ppm 

 and l/IO males that received 300 ppm died be- 

 fore the end of the studies (Table 20). The final 

 mean body weight of mice that received 5,000 

 ppm was 13% lower than that of the controls for 

 males and 15% lower for females. Estimated 

 feed consumption by dosed groups was similar 

 to that by controls. The urine of mice that re- 

 ceived 5,000 ppm was bright yellow. Inactivity, 

 hypothermia, and sunken eyes were observed 

 in mice that received 5,000 ppm but not in 

 those that received 2,500 ppm. Minimal-to 

 mild degeneration of the germinal epithelium 

 of the testis (accompanied by aspermatogene- 



sis) was observed in all males that received 

 1,300, 2,500, or 5,000 ppm; necrosis of the ovar- 

 ian follicle was observed in 8/10 females that 

 received 5,000 ppm but not in those that re- 

 ceived lower doses. Minimal-to-mild necrosis of 

 the kidney epithelium was observed in 2/9 

 males that received 5,000 ppm. The liver 

 weight to body weight ratios were not affected 

 by administration of nitrofurantoin (Table 21). 



Dose Selection Rationale: Because of lower 

 mean body weight gain in males and females at 

 higher concentrations and kidney necrosis and 

 deaths in males at 5,000 ppm, dietary concen- 

 trations selected for mice in the 2-year studies 

 were 1,300 and 2,500 ppm nitrofurantoin. 



(a) Number surviving/number initially in the group 



(b) Initial group mean body weight ± standard error of the mean. Subsequent calculations are based on those animals 

 surviving to the end of the study. 



(c) Mean body weightchange ofthe survivors ± standard error of the mean 



(d) Grams of feed consumed per animal per day; not corrected for scatter. 

 (e)Weel( of death: 11 



(fiWeelt of death: 2,2 



Nitrofurantoin, NTP TR 341 



50 



