Cardioprotective Effects of the 4-Week Aerobic Running Exercises Before Treatment with Doxorubicin in Rats.

Doxorubicin is associated with cardiotoxicity, and physical exercise seeks to minimize the toxic effects of doxorubicin through physiological cardiac remodeling, as well as the reduction of oxidative stress, evidenced by previous studies. This study aimed to analyze whether running training before treatment with doxorubicin influences tolerance to physical exertion and cardiotoxicity. Thirty-nine male Wistar rats, aged 90 days and weighing between 250 and 300 g, were divided into 4 groups: Control (C), Doxorubicin (D), Trained (T), and Trained + Doxorubicin (TD). Animals in groups T and DT were submitted to treadmill running for 3 weeks, 5 times a week at 18 m/min for 20-30 min before treatment with doxorubicin. Animals in groups D and DT received intraperitoneal injections of doxorubicin hydrochloride three times a week for two weeks, reaching a total cumulative dose of 7.50 mg/kg. Our results show an increase in total collagen fibers in the D group (p = 0.01), but no increase in the TD group, in addition to the attenuation of the number of cardiac mast cells in the animals in the TD group (p = 0.05). The animals in the TD group showed maintenance of tolerance to exertion compared to group D. Therefore, running training attenuated the cardiac damage caused by the treatment with doxorubicin, in addition to maintaining the tolerance to exertion in the rats.

Leucine Supplementation Improves Effort Tolerance of Rats With Hyperthyroidism.

Leucine is a regulator of protein metabolism in vivo and information on its action on effort tolerance of both animals and humans with hyperthyroidism is scarce. The objective of the present study was to verify the influence of leucine supplementation on the effort tolerance of Wistar rats with experimental hyperthyroidism. 40 animals were divided into four groups of ten: control (C), hormone (H), leucine (L), and hormone + leucine (HL). Hyperthyroidism was induced by daily administration of 20 µâ‹…g100 g-1 of levothyroxine sodium in aqueous suspension by gavage. Leucine was supplemented by adding 5% of the amino acid to the conventional feed. The animals' blood was collected by cardiac puncture to analyze TSH, T4, and T3 levels. The effort tolerance was determined by the swimming test with a 7% load attached to animals' tails. Statistical analysis was performed using the Shapiro-Wilk normality test, followed by the analysis of variance (ANOVA) of repeated measures of two factors (treatment × time) and Tukey post hoc, with a significance level of p < 0.05. Administering thyroid hormone increased the swimming performance of rats after 14 and 21 days, but with a drop in performance at 28 days. The HL group, on the other hand, had a significantly higher swimming performance compared to the other groups after 28 days of treatment. Leucine supplementation associated with the experimental model of hyperthyroidism improved the performance of rats in a swimming test after 28 days of treatment.