Summary We investigated the effect of training on the Na+, K+‐ATPase concentration in foal skeletal muscle by measurement of [3H]ouabain binding. From the 7th day after birth, 12 foals were divided in 3 groups: a) staying in a box stall (Box); b) staying in a box stall with a training regimen of an increasing number of sprints per day (Training); and c) staying on pasture (Pasture). Euthanasia was performed after 5 months. In semitendinosus muscle, the concentration of [3H]ouabain binding sites (pmol/g wet wt) was 181 ± 6 in the Box, 220 ± 15 in the Training, and 197 ± 8 in the Pasture group (all n = 6; Box vs. Training, P<0.05). In gluteus medius, the concentration of [3H]ouabain binding sites was 168 ± 9 in the Box, 219 ± 12 in the Training, and 175 ± 4 in the Pasture group (all n = 6; Box or Pasture vs. Training, P<0.02). Scatchard analysis of saturation curves showed that the difference in [3H]ouabain binding sites between the 3 groups could not be ascribed to differences in the Kd for ouabain. Both for semitendinosus and gluteus medius muscle, the concentration of [3H]ouabain binding sites increased in the order Box < Pasture < Training (a total increase of around 20%). This suggests a specific effect of the amount and intensity of exercise on the Na+, K+ ‐ATPase concentration in horse skeletal muscle, and may lead to a better performance during exercise.

Objective: To examine the ameliorative effect of rice bran hydrolysates (RBH) on metabolic disorders, cardiac oxidative stress, heart rate variability (HRV), and cardiac structural changes in high fat and high fructose (HFHF)-fed rats. Methods: Male Sprague-Dawley rats were daily fed either standard chow diet with tap water or an HFHF diet with 10% fructose in drinking water over 16 weeks. RBH (500 and 1 000 mg/kg/day) was orally administered to the HFHF-diet-fed rats during the last 6 weeks of the study period. At the end of the treatment, metabolic parameters, oxidative stress, HRV, and cardiac structural changes were examined. Results: RBH administration significantly ameliorated metabolic disorders by improving lipid profiles, insulin sensitivity, and hemodynamic parameters. Moreover, RBH restored HRV, as evidenced by decreasing the ratio of low-frequency to high-frequency power of HRV, a marker of autonomic imbalance. Cardiac oxidative stress was also mitigated after RBH supplementation by decreasing cardiac malondialdehyde and protein carbonyl, upregulating eNOS expression, and increasing catalase activity in the heart. Furthermore, RBH mitigated cardiac structural changes by reducing cardiac hypertrophy and myocardial fibrosis in HFHF-diet-fed rats. Conclusions: The present findings suggest that consumption of RBH may exert cardioprotective effects against autonomic imbalances, cardiac oxidative stress, and structural changes in metabolic syndrome.

In horses, the activation of skeletal muscle Na+,K(+)-ATPase during exercise is likely to decrease with age. Training appears to result in an increase in Na+,K(+)-ATPase activity in skeletal muscle with subsequent upregulation of Na+,K(+)-ATPase concentration if the existing Na+,K(+)-ATPase capacity cannot meet requirements.

We determined the effects of food supply and lowintensity training on growth, serum thyroid hormone levels and the Na + ,K + -pump concentration in equine skeletal muscle. Twenty-two Shetland ponies were subjected to two different feeding regimes for 2½ years (11 ponies per group): food restriction (body condition score kept at 2) or ad libitum fed (body condition score kept at 8). Five ponies in each group underwent low-intensity training. Gluteus medius muscle and serum samples were obtained in April 1998. Subsequently, all ponies were fed ad libitum and the training programme was stopped. Muscle biopsies and serum samples were collected again in November 1998.Food restriction was associated with a 30-50% reduction of body weight gain. While the total thyroxine (T 4 ) level was increased, the free T 4 remained at the control level. The serum total tri-iodothyronine (T 3 ) and free T 3 were reduced by 30% and 49% respectively. After 6 months of refeeding there were no differences in any of the hormone levels between the ad libitum fed and the food-restricted groups. Food restriction produced a minor, but not significant, decrease in the Na + ,K + -pump concentration in the gluteus medius muscle of the Shetland ponies. Lowintensity training reduced weight gain of the ad libitum fed group by 25%, but had no detectable effect on the concentration of the Na + ,K + -pumps. We conclude that prolonged food restriction in Shetland ponies results in a weight gain reduction of 30-50%, and is associated with similar decreases in serum total and free T 3 . The reduction in serum T 3 only slightly influenced the Na + ,K + -ATPase concentration in skeletal muscle, indicating that muscle tissue of different species may respond differently to changes in circulating thyroid hormones.

Summary The purpose of the present study was to determine whether training and detraining affect the Na+, K+‐ATPase concentration in horse skeletal muscles, and whether these effects are specific for the muscles involved in the training programme. Twenty‐four Dutch Warmblood foals age 7 days were assigned randomly to 3 groups: Box (box‐rest without training), Training (box‐rest with training: short‐sprint) and Pasture (pasture without training). Exercise regimens were carried out for 5 months and were followed by 6 months of detraining. Five of the foals in each group were subjected to euthanasia at age 5 months and the remaining foals at 11 months. Muscle samples were collected from the deep part of the gluteus medius, semitendinosus and masseter muscles. The Na+, K+‐ATPase concentration was quantified by [3H]ouabain binding. In the Training group, the concentration of Na+, K+‐ATPase in gluteus medius and semitendinosus muscle, but not in masseter muscle, showed a relative increase of 20% (P<0.05) as compared to Box foals. After detraining for the subsequent 6 months, the concentration of Na+, K+‐ATPase in semitendinosus muscle remained the same, while that in gluteus medius muscle was reduced by 10%. It is concluded that: 1) short‐sprint training for 5 months induced an increase of the Na+, K+‐ATPase concentration in gluteus medius and semitendinosus muscles of the foal. Interestingly, this effect persisted during the 6 months of the detraining period. Whether the higher Na+, K+‐ATPase concentration due to training of young foals leads to a better athletic performance when they become mature still needs to be established; 2) the factors that initiate an increase in Na+, K+‐ATPase concentration following training are likely to be located in the muscle itself and 3) the training effect may last for several months after returning to normal activity, especially in muscles containing a high percentage of fast‐twitch fibres.