Exposure to light-at-night increases mammary tumors

[lilangel]

I was reading and talking with Digi about lights on all night long around your rats and i know i read somewhere that lights can cause mammary tumors in rats.

Here is a page i did find about it.

Exposure to light-at-night increases the growth of DMBA-induced mammary adenocarcinomas in rats

Abstract
In order to assess whether light exposure at night influences the growth of mammary tumors, as well as the role of melatonin in this process, female rats bearing DMBA-induced mammary adenocarcinomas were exposed to different lighting environments. Animals exposed to light-at-night, especially those under a constant dim light during the darkness phase, showed: (a) significantly higher rates of tumor growth as well as lower survival than controls, (b) higher concentration of serum estradiol, and (c) lower nocturnal excretion of 6-sulfatoxymelatonin, without there being differences between nocturnal and diurnal levels. These results suggest that circadian and endocrine disruption induced by light pollution, could induce the growth of mammary tumors.

http://www.sciencedirect.com/science?_o ... 14c513d98c

 

[jorats]

We should take note that in the study they induced *malignant* mammary tumours. Our rats are prone to benign mammary tumours so this study does not claim that light exposure at night can cause our rats to have mammary tumours. It only encourages the growth of malignant ones but further study would be required to determine the effects of light exposure at night on benign tumours.

However rats do have a natural circadian rhythm that should not be disrupted by constant light.
And to play it safe with benign tumours, keep the lights out at night, or at least the study has been expended to include benign tumours.

 

[SQ]

Rats need an 8 hour period of complete darkness every 24 hours.