III. RESULTS: RATS 



THIRTEEN-WEEK STUDIES 



One of 10 female rats that received 10,000 ppm 

 died before the end of the studies (Table 7). The 

 final mean body weights of rats that received 

 2,500, 5,000, or 10,000 ppm were 10%, 34%, or 

 47% lower than that of the controls for males 

 and 15%, 31%, or 41% lower for females. Feed 

 consumption by dosed and control groups was 

 generally similar. The urine of dosed rats was 

 bright yellow. Minimal-to-mild degeneration of 

 the germinal epithelium of the seminiferous tu- 

 bules of the testis with aspermatogenesis was 

 observed in 29/30 males that received 2,500 ppm 



or more. Minimal-to-mild necrosis of the ovari- 

 an follicles was observed in 8/10 females that 

 received 10,000 ppm, and minimal necrosis was 

 observed in 3/10 females that received 5,000 

 ppm and 1/10 females that received 2,500 ppm 

 The liver weight to body weight ratios for rats 

 that received 5,000 or 10,000 ppm were signif- 

 icantly greater than those of controls (Table 8) 



Dose Selection Rationale: Because of lower body 

 weight gain at higher concentrations, dietary 

 concentrations selected for rats for the 2-year 

 studies were 1,300 and 2,500 ppm nitrofurantoin 

 for males and 600 and 1 ,300 ppm for females 



TABLE 7. SURVIVAL, MEAN BODY WEIGHTS, AND FEED CONSl'MPTION OF RATS IN THE 

 THIRTEEN-WEEK FEED STUDIES OF NITROFURANTOIN 



(a) Number surviving/number initially in the group 



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

 surviving to the end of the study. 



(cl Mean body weight change of the survivors ± standard error of the mean 



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



(e) Week of death: 12 



37 



Nitrofurantoin, NTP TR 341 



