Authors
Caratero A. Courtade M. Bonnet L. Planel H. Caratero C.
Institution
Laboratoire d'Histologie-Embryologie-Cytogenetique, Faculte de Medecine
Toulouse-Rangueil, Toulouse, France. caratero@cict.fr
Title
Effect of a continuous
gamma irradiation at a very low dose on the life span of
mice.
Source
Gerontology. 44(5):272-6, 1998.
Abstract
BACKGROUND: There is epidemiological evidence that suggests there are
beneficial effects of ionizing radiation at low doses. Some
experimental studies confirmed this hormetic effect with
doses of about 1 cGy/day, but no data concerning very low dose rates are
available. OBJECTIVE: The aim of this study was to determine the life span of
mice exposed to very low doses of ionizing radiation. METHODS: Six hundred
female C57BL/6 mice, 1 month old, were exposed to chronic
gamma irradiation at very low dose rates of 7 or 14
cGy/year. These doses are about 25 or 50 times higher than background, but
much lower than the doses of about 1 cGy/day used in previous experiments.
Three hundred mice living in the same room were used as controls. RESULTS:
The life span, after the beginning of the experiment, determined by the
survival time of 50% of each population, is increased in irradiated mice: 549
days in controls, 673 days in both irradiated groups. The differences are
significant between the control and the irradiation mice. Differences between
mice irradiated with 7 or 14 cGy are not significant. CONCLUSIONS: These
results confirm the possibility of a nonharmful effect
(hormesis) of ionizing radiation. They demonstrate that the paradigm, which
states that low-dose effects can be predicted high-dose
effects, cannot be systematically applied in radiation
biology in general and gerontology in particular.