Radiation hormesis, when total-body irradiation
(TBI) is administered at a cumulative dose of 1.5 Gy at around 0.1 Gy/day, has
recently been considered a type of useful cancer therapy. Many studies have
linked hormesis to immune system potentiation. The aim of this research was to
examine the impact of natural variation on the signs of hormesis in the regenerative
state of dog tissues, which are visible across the life span following complete
body exposure to low daily doses of external gamma radiation. Ninety beagle
dogs of both sexes, from 1 year after birth to death, were irradiated with
cobalt 60 at 0.003 Gy/day. Control (n = 169) and irradiated animals
underwent clinical examination and autopsy during their entire life and were
then retrospectively divided into two subgroups with (W) or without benign
tumors or tumors of unknown nature (WO) that were clinically reported
throughout the entire lifespan on a single day. Radiation hormesis was observed
only in subgroup WO, which in the absence of radiation had a life span (LS) of
10.7 years. In the WO subgroup (p<0.05), the radiogenic prolongation of life
to 11.8 years was close to that in the W control and irradiated W subgroups
(11.8 and 11.5 years, respectively). The number of solid malignancies found in the control WO subgroup upon
autopsy was smaller (39.5%) than that evident in the control W subgroup (60
percent ). The irradiation of the WO subgroup was followed by a small increase
(1.14-fold) in the amount of solid malignancies visible during autopsy and in
the clinical signs of tissue atrophy and body weight loss (2.4-fold and
2.4-fold respectively) relative to the irradiated W subgroup, but was
accompanied by a sharp decrease in the degree of anemia and hematoblastosis
(>10-fold for both). The
data exclude the notion that radiation is associated with recovery, but suggest
that only in poorer animals can such pathologies (e.g., hematoblastosis) be
replaced with other less severe somatic diseases. It implies that, at least in
mammals, the notion of radiobiological "stimulation" is unacceptable.
Author(s) Details
Aleksey N. Shoutko
Laboratory for Improvement of the
Radiation Treatment Methods, Granov’ Russian Research Center for Radiology and
Surgical Technologies, 197758, 70, Leningradskaya str., Pesochny, St.
Petersburg, Russia.
Ludmila P. Ekimova
Laboratory for Improvement of the Radiation Treatment Methods, Granov’
Russian Research Center for Radiology and Surgical Technologies, 197758, 70,
Leningradskaya str., Pesochny, St. Petersburg, Russia.
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