Effects of X-ray irradiation and housing conditions on mitochondria in Peromyscus maniculatus

Challenging environmental conditions, such as exposure to ionizing
radiation, can induce oxidative stress within mitochondria. However,
organisms show variation in their capacity to cope with cellular stress.
This study aimed to identify how housing conditions influence
mitochondrial stress responses under exposure to radiation. We used North
American deer mice (Peromyscus maniculatus), kept in standard rodent boxes
or large semi-natural enclosures that allowed for natural levels of
physical activity and social structures under ambient atmospheric
conditions. Animals from each housing condition were exposed to 2000 mSv
(2 Gy) of ionizing X-ray radiation, a dose comparable to long-term
spaceflight. Animals were euthanized for analysis prior to irradiation
(baseline), within four days post-irradiation, or one-month following
irradiation. Relative mass of the liver was lower than the baseline for
irradiated animals maintained in the semi-natural enclosures. State 4 and
coupled and uncoupled state 3 respiratory capacity of liver and skeletal
muscle mitochondria were lower four days after the exposure. Yet, a month
after exposure these variables were comparable to baseline in muscle but
remained lower in the liver. The mitochondrial volume was lower after
irradiation relative to baseline and was higher in animals maintained in
standard rodent boxes, in both tissues. Oxidative damage to lipids in
liver was higher in animals kept in boxes, whereas in muscle it was higher
in animals kept in the semi-natural enclosures, and oxidative damage to
proteins did not change. These results suggest that a heterogenous
environment with greater potential for activity may counter the effects of
ionizing radiation, although this effect appears to be modest.