[Lighting effect on spontaneous tumor development in female rats].

The investigation is concerned with effects of lighting--12hr light/12hr dark (standard), natural lighting in the Russian North-West, constant illumination and light deprivation--on life span and spontaneous tumor development in female LIO rats. Constant and North-West lighting involved premature aging, shorter mean (13.5 and 25%) and maximum life span (by 9 and 7 months, respectively) and a significant increase in spontaneous tumor development rate as compared with standard lighting. Light deprivation resulted in a longer maximum life span and significant (2.1 times) drop in tumor incidence.