Exercícios físicos de alta intensidade agudo e crônico inibem o esvaziamento gástrico de líquidos em ratos : papel da academia e de via neuro-humoral

Abstract

In the recent years, there is a general consensus on the benefits of regular physical activity on health caliber, prevention and treatment of various chronic diseases besides improving general quality of life. Specifically, physical activity of varied intensities broadly influence vital physiological systems involving the neuromuscular system (promoting increased muscle strength and mass) cardiovascular (induced basal bradycardia at rest), endocrine (favoring the release of several hypothalamic hormones) and even the gastrointestinal system. Published literature report that depending on the intensity and volume of exercise, changes in blood volume may result to associated gastrointestinal ischemia, which would possibly alter gastrointestinal motility. However, the mechanisms involved in altered gastrointestinal motility due to exercise are yet to be fully elucidated. Thus, the objective of this study was to investigate the effect of acute and chronic exercise on gastric emptying of liquids, as well as explain the possible mechanisms involving acid-base balance and subsequent neurohumoral pathways. Male Wistar rats (180 to 250g), were obtained from the vivarium of the Department of Physiology and Pharmacology, University Federal do Ceara. They were initially assigned to adapt to either acute or chronic exercise protocols. The acute exercise protocol adaptation consisted of collective swimming in a bath tub over increasing scale periods over 5 days, with a single and final swim 48hs after the fifth day, with a 5% body weight load so as to exploit the lactate threshold. The chronic exercise protocol consisted of collective swimming in a bath tub over 5 days without a specific time count pattern. Forty-eight hours after this adaptation, they were submitted to exercise protocol jumps (4x10 30sec interval, 5days/week/4weeks). After a session of intense exercise, we evaluated gastric emptying, blood analysis, hemodynamic and neurohumoral mechanisms related to hormones 5-HT, OT and CCK as well as the gene expression of these hormones in gastrointestinal tissues. In chronic exercised animals, we evaluated gastric emptying, intestinal transit, gastric compliance and hemodynamic parameters. We found that both acute and chronic exercise promoted a significant decrease (p <0.05) gastric emptying of liquids. Moreover, chronically exercised rats had significant (p <0.05) increased gastric compliance, when compared to sedentary rats; but no change in the intestinal transit. When compared to sedentary rats, acute exercised mice showed metabolic acidosis with a significant decrease (p <0.05) in pH values due to low bicarbonate. This change in acid-base balance was significantly (p <0.05) prevented with pretreating the animals to an oral dose of NaHCO3 (500mg/kg) 40min before exercise. We also observed that pretreatment with OT antagonist and CCK significantly prevented (p <0.05) the decrease in gastric emptying induced by acute exercise. Acute exercise decreased significantly (p <0.05) values for the gene expression of hormones OT and ANP in the fund and pylorus of the rats, when compared to sedentary rats. On the other hand, we found that acute exercise significantly (p <0.05) increased CCK-gene expression values in the fund, pylorus and duodenum of rats, in comparison to sedentary. Concluding, exercise induced changes in gastric motility in both acute and chronic exercise protocols. The pre-treatment with NaHCO3, Atosibana, and Ondansetron Devazepide prevented the decrease in gastric emptying induced by acute exercise. We suggest that dysmotility induced by exercise may be influenced by a pathway related to oxytocin, serotonin and cholecystokinin, which too have a role in the acid-base homeostasis.