Effects of high intensity physical training on endocrine and metabolic aspects of Wistar rats

Abstract

The aims of this study were: 1) to investigate the endocrine-metabolic adaptations, related to carbohydrate and protein metabolism in rats submitted to high intensity training; 2) to analyze the relationship of these adaptations with the stress mechanisms in rest and post-exercise conditions. Male Wistar rats were separated into 4 groups: sedentary-rest (SR), trained-rest (TR), sedentary submitted to acute exercise (SA) and trained submitted to acute exercise (TA). During 6 weeks TR and TA groups performed 4 sets of 10 jumps/day, 5d/wk, in a swimming-pool, supporting a load of 50% of body mass. At the 5th week rats were submitted to glucose (GTT) and insulin (ITT) tolerance tests, load test, and vanilmandelic acid (AVM) test. At the end of the sixth week rats were sacrificed in both rest and post-exercise conditions. Blood samples were collected to determine ACTH, corticosterone, FFA, insulin and glucose. Hepatic, muscular and cardiac tissues were used to determine glycogen, protein and DNA. Adrenals were excised to determine cholesterol and ascorbic acid contents, and to measure the adrenal area. The results were analyzed by t-Student test, ANOVA, and Bonferroni post-hoc where appropriate and the significance level was 5%. The results indicate that training didn't result in significant modifications in serum glucose and insulin during oral GTT in the rest condition. However, the trained group showed higher glucose disappearance rate during the ITT when compared to sedentary. Training promoted increase in muscle glycogen store, even after acute exercise. Both S and T groups showed protein mobilization after acute effort. Acute exercise resulted in increases in glycaemia and decreases in insulinaemia in both S and T groups. ACTH suffered significant increase at the acute effort, mainly in sedentary group. Only the trained group showed increase of corticosterone in post-exercise condition. No differences were observed in urinary AVM and in adrenal cholesterol concentration, as well as in adrenal medulla, cortex and total area. Adrenal ascorbic acid increased by acute exercise in sedentary and trained rats. These results led us to conclude that: 1) high intensity physical training promoted increase of energy stores in muscle; 2) acute exercise favored glycogen and protein mobilization in both sedentary and trained groups; 3) acute effort promoted reduction in serum insulin, and increase of plasma ACTH; 4) sedentary and trained rats showed differences in stress hormones response after acute exercise; 5) the proposed physical training seems not to result in stress to exercised animals, but in post-exercise condition physical training modulated the hipotalamic-pituitaric-adrenal axis. Key words: high intensity physical training, metabolism, stress.