Objectives—To determine effects of dietary antioxidant
supplementation on plasma concentrations of
antioxidants, exercise-induced oxidative damage, and
resistance to oxidative damage during exercise in
Alaskan sled dogs.
Animals—62 Alaskan sled dogs.
Procedure—Dogs were matched for age, sex, and ability
and assigned to 1 of 3 groups: sedentary and nonsupplemented
(control [C]; n = 21), exercised and supplemented
(S; 22), and exercised and nonsupplemented
(N; 19). Dogs in group S were given 400 units of α-
tocopherol acetate, 3 mg of β-carotene, and 20 mg of
lutein orally per day for 1 month, then dogs in groups S
and N completed 3 days of exercise. Blood samples
were collected before and after 1 and 3 days of exercise
and after 3 days of rest. Plasma antioxidant concentrations
were determined, and oxidative damage to DNA
(plasma 7,8 dihydro-8-oxo-2'deoxyguanosine [8-oxodG]
concentration) and membrane lipids (plasma hydroperoxide
concentration) and resistance of plasma lipoproteins
to oxidation were assessed.
Results—Supplementation increased plasma concentrations
of α-tocopherol, β-carotene, and lutein.
Plasma concentration of α-tocopherol increased
and concentration of lutein decreased in group S
with exercise. Concentration of 8-oxodG decreased
in group S but increased in group N during and after
exercise. Lag time of in vitro oxidation of lipoprotein
particles increased with exercise in group S only.
Conclusions and Clinical Relevance—Dietary supplementation
with antioxidants resulted in increased plasma
concentrations of antioxidants. Moreover, supplementation
decreased DNA oxidation and increased
resistance of lipoprotein particles to in vitro oxidation.
Antioxidant supplementation of sled dogs may attenuate
exercise-induced oxidative damage. (Am J Vet Res
Objective—To determine whether dietary antioxidants
would attenuate exercise-induced increases in
plasma creatine kinase (CK) activity in sled dogs.
Animals—41 trained adult sled dogs.
Procedure—Dogs, randomly assigned to 2 groups,
received the same base diet throughout the study.
After 8 weeks on that diet, 1 group (21 dogs) received
a daily supplement containing vitamins E (457 U) and
C (706 mg) and β-carotene (5.1 mg), and a control
group (20 dogs) received a supplement containing
minimal amounts of antioxidants. After 3 weeks, both
groups performed identical endurance exercise on
each of 3 days. Blood samples were collected before
and 3 weeks after addition of supplements and after
each day of exercise. Plasma was analyzed for vitamins
E and C, retinol, uric acid, triglyceride, and cholesterol
concentrations, total antioxidant status (TAS),
and CK activity.
Results—Feeding supplements containing antioxidants
caused a significant increase in vitamin E concentration
but did not change retinol or vitamin C concentrations
or TAS. Exercise caused significantly higher
CK activity, but did not cause a significant difference
in CK activity between groups. Exercise was
associated with significantly lower vitamin E, retinol,
and cholesterol concentrations and TAS but significantly
higher vitamin C, triglyceride, and uric acid concentrations
in both groups.
Conclusions and Clinical Relevance—Use of supplements
containing the doses of antioxidants used
here failed to attenuate exercise-induced increases in
CK activity. Muscle damage in sled dogs, as measured
by plasma CK activity, may be caused by a
mechanism other than oxidant stress. (Am J Vet Res