Chronic aerobic swimming exercise promotes functional and morphological changes in rat ileum

Several studies have reported the gastrointestinal (GI) effects promoted by the physical exercise. Thus, we aimed to evaluate the influence of swimming exercise on the contractile reactivity, lipid peroxidation and morphology of rat ileum. Wistar rats were divided into sedentary (SED) and groups exercised for two (EX2), four (EX4), six (EX6) or eight (EX8) weeks, 5 days/week. Animals were killed; the ileum was removed and suspended in organ baths where the isotonic contractions were recorded. Lipid peroxidation was evaluated by MDA (malondialdehyde) measurement with TBARS (thiobarbituric acid reactive substances) assay and morphology by histological staining. Cumulative concentrationresponse curves to KCl were attenuated, as the E-max values were changed from 100% (SED) to 63.1+/-3.9 (EX2), 48.8+/-3.8 (EX4), 19.4+/-1.8 (EX6) and 59.4+/-2.8% (EX8). Similarly, cumulative concentration-response curves to carbamylcholine hydrochloride (CCh) were attenuated, as the E-max values were changed from 100% (SED) to 74.1+/-5.4 (EX2), 75.9+/-5.2 (EX4) and 62.9+/-4.6 (EX6), but not in the EX8 (89.7+/-3.4%). However, CCh potency was increased in this latter, as the EC50 was altered from 1.0+/-0.1x10(-6) (SED) to 2.1+/-0.4x10(-7) (EX8). MDA concentration was altered only in EX4 (44.3+/-4.4) compared with SED (20.6+/-3.6 mu mol/l). Circular layer was reduced in SED when compared with the exercised groups. Conversely, longitudinal layer was increased. In conclusion, chronic swimming exercise reduces the ileum contraction, equilibrates the oxidative damage and promotes changes in tissue size to establish an adaptation to the exercise.