Je. Grundy et Kb. Storey, ANTIOXIDANT DEFENSES AND LIPID-PEROXIDATION DAMAGE IN ESTIVATING TOADS, SCAPHIOPUS-COUCHII, Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology, 168(2), 1998, pp. 132-142
Tissue-specific changes in antioxidant defenses and lipid peroxidation
damage were analyzed in spade-foot toads. Scaphiopus couchii, to dete
rmine how these responded during estivation, a state of suppressed oxy
gen consumption. Maximal activities of glutathione-S-transferase, glut
athione reductase, glutathione peroxidase, superoxide dismutase and ca
talase were measured in sis organs from 3-month-estivated toads and co
mpared with activities in animals awakened for 10 days after estivatio
n. Activities of many enzymes, particularly the glutathione-linked enz
ymes, were significantly lower in tissues of estivating toads than in
awake toads, This indicates that enzymatic antioxidant defenses are pr
obably modulated in response to the rate of reactive oxygen species ge
neration in tissues, which is proportional to oxygen consumption. Anti
oxidant enzyme activities were largely insensitive to high urea, which
accumulates during estivation-but were inhibited by elevated KCI. Lev
els of reduced glutathione were also significantly lower in three orga
ns during estivation and all organs, except skeletal muscle, exhibited
a higher oxidized/reduced glutathione ratio, indicating a more oxidiz
ed state during estivation. Products of lipid peroxidation (conjugated
dienes, lipid hydroperoxides) were higher in tissues of estivated tha
n control toads, suggesting accumulated oxidative damage to lipids dur
ing dormancy. One enzymatic source of free radical generation, xanthin
e oxidase, appeared to have little impact because its activity was del
ectable only in liver and was significantly lower in estivated toads.
The data indicate that both enzymatic and metabolite antioxidant defen
ses in toads are adaptable systems that are modulated in estivating ve
rsus awake states.