SCANNING ELECTRON MICROSCOPIC OBSERVATIONS ON PRENEOPLASTIC AND NEOPLASTIC LESIONS OF THE TRACHEA IN SYRIAN GOLDEN HAMSTERS INDUCED BY DIETHYLNITROSAMINE

Abstract

Ultrastructural observations by scanning electron microscope (SEM) of pre- or neoplastic tracheal lesions in Syrian golden hamsters induced by diethylnitrosamine (DEN) were investigated. Twenty five, six-week-old, male Syrian golden hamsters were injected subcutaneously twice a week for 12 weeks with 18mg/kg body weight of DEN. Six hamsters were injected only vehicle and served as control. At weeks 2, 4, 8, 12, and 16, 5 hamsters of DEN treated group were sacrificed. At weeks 2, 8, and 12, hamsters of vehicle control group were also sacrificed. Sequential changes of tracheal tumors were investigated by ultrastructural and histopathological observations. At week 2, a focal loss of cilia from surface cells of the trachea of DEN treated hamster were already detected by SEM. At week 4, decilinated changes of the surface became more markedly, and at week 8, various kinds of preneoplastic and neoplastic changes were observed in trachea of DEN treated hamster. Those changes could be detected by microscopy as well as SEM. By week 16, papillary tumors were found in all animals treated with DEN. No changes were observed in trachea of control animals. These results showed that scanning observations can detect the very early lesions of trachea and it is a very useful method especially for detecting the changes of tracheal lesions on hamster tracheal carcinogenesis.