Objective—To characterize insulin-sensitive glucose-transporter (GLUT-4) protein in equine tissues
and determine effects of exercise and glucose administration
on content of GLUT-4 protein in equine skeletal
Sample Population—Tissue samples from 9 horses.
Procedure—Western blot analyses were performed
on crude membrane preparations of equine tissues to
characterize GLUT-4. In a crossover, randomized
study, horses were strenuously exercised for 3 consecutive
days and then administered 13.5% glucose
or isotonic saline (0.9% NaCl; control) solution, IV, at
similar infusion rates for 12.1 hours. Samples were
collected from the middle gluteal muscle before and
after exercise and 10.1 hours after completion of an
infusion and used for measurements of glycogen
concentration and total content of GLUT-4 protein.
Results—Immunoblot analyses detected specifically
immunoreactive bands for GLUT-4 in insulin-sensitive
tissues. Content of GLUT-4 protein in skeletal muscle
increased significantly by 27.3 and 12.3% 22.2 hours
after exercise for control and glucose groups, respectively.
Intravenous infusion of glucose resulted in a
significantly higher rate of glycogenesis, compared
with results for the control group (mean ± SD,
3.98 ± 0.61 and 1.47 ± 0.20 mmol/kg/h, respectively).
Despite enhanced glycogenesis, we did not detect an
increase in content of GLUT-4 protein after glucose
infusion, compared with values after exercise.
Conclusions and Clinical Relevance—GLUT-4 protein
was expressed in equine skeletal and cardiac
muscles. Exercise increased total content of GLUT-4
protein in skeletal muscle, and replenishment of muscle
glycogen stores after glucose infusion attenuated
the exercise-induced increase in the content of
GLUT-4 protein in equine skeletal muscle. (Am J Vet Res 2003;64:1500–1506)
Objective—To determine neurologic indications associated with abnormal results for computed tomography (CT) imaging of the head of horses affected by neurologic disorders.
Design—Retrospective case series.
Procedures—Signalment, history, clinical abnormalities, and clinicopathologic findings were obtained from medical records of horses examined because of neurologic disorders, and precontrast and postcontrast CT images of the head were reviewed. Data were analyzed by use of univariate and multivariate logistic regression.
Results—For a horse with abnormal mentation, odds of having abnormal results for CT imaging of the head was 30 times (95% confidence interval [CI], 2.36 to 374.63) the odds for a similar horse without abnormal mentation. For a horse with cranial nerve deficits, odds of having abnormal results for CT imaging of the head was 11 times (95% CI, 1.00 to 127.96) the odds for a similar horse without cranial nerve deficits. For a horse with seizure-like activity, odds of having abnormal results for CT imaging of the head was 0.05 times (95% CI, 0 to 0.90) the odds for a similar horse without seizures.
Conclusions and Clinical Relevance—These results suggested that alterations in consciousness and cranial nerve deficits were strong predictors of abnormal CT findings for the head of affected horses. Thus, CT can be a useful complementary diagnostic test in horses with these neurologic deficits. In contrast, alternative diagnostic tests (eg, electroencephalography and magnetic resonance imaging) should be considered in horses with seizure-like activity that do not have head trauma or cranial nerve deficits.
Objectives—To determine effects of feeding diets
with various soluble-carbohydrate (CHO) content on
rates of muscle glycogen synthesis after exercise in
Animals—7 fit horses.
Procedures—In a 3-way crossover study, horses
received each of 3 isocaloric diets (a high soluble CHO
[HC] diet, a low soluble CHO [LC] diet, or a mixed soluble
CHO [MC] diet). For each diet, horses were subjected
to glycogen-depleting exercise, followed by feeding
of the HC, LC, or MC diet at 8-hour intervals for 72
Results—Feeding the HC diet resulted in a significantly
higher glycemic response for 72 hours and significantly
greater muscle glycogen concentration at 48 and
72 hours after exercise, compared with results after
feeding the MC and LC diets. Muscle glycogen concentrations
similar to baseline concentrations were
detected in samples obtained 72 hours after exercise in
horses when fed the HC diet. Rate of glycogen synthesis
was significantly higher when horses were fed
the HC diet, compared with values when horses were
fed the MC and LC diets. Glycogen synthase activity
was inversely related to glycogen content. Protein content
of glucose transporter-4 was the lowest at 72
hours after exercise when horses were fed the HC diet.
Conclusions and Clinical Relevance—Muscle glycogen
synthesis was slower after glycogen-depleting
exercise in horses, compared with synthesis in
humans. Feeding HC meals after strenuous exercise
hastened replenishment of muscle glycogen content,
compared with results for feeding of LC and MC
diets, by increasing availability of blood glucose to
skeletal muscles. (Am J Vet Res 2004;65:916–923)