Induction of esophageal cancers by nitenpyram (NIT) in rats

This study was made to investigate and evaluate the safety and carcinogenicity of nitenpyram (NIT) in rats.

A totally 50 male and 50 female SD rats were treated with NIT at 0, 800, 2400, and 7200 ppm, respectively, for 104 w. The growth, clinical signs, and survival rates, as well as the body and organ weights of these animals, were analyzed. Histopathological examination was also performed.

Compared with the control group, survival rates at 104 w were significantly decreased in the 7200 ppm dose group, for both the male and female animals. The occurrence of esophageal squamous papilloma (ESP) was significantly increased in the treated animals. The occurrences of ESP for the 0, 800, 2400, and 7200 ppm NIT treatment groups were 0/39, 0/39, 3/35, and 9/27 for the male animals, and 0/43, 0/43, 6/49, and 12/33 for the female animals, respectively. For pre-neoplastic lesion of ESP, the occurrences of esophageal squamous hyperplasia for the 0, 800, 2400 and 7200 ppm NIT treatment groups were 0/39, 1/39, 10/35, and 9/27 for the male animals, and 0/43, 2/43, 15/49, and 17/33 for the female animals, respectively. The basal cell hyperplasia from mild to severe degrees was observed in the treatment groups.

NIT exhibits carcinogenicity of ESP in the male and female rats after the two-year treatment.