title: Long-term swimming in an inescapable stressful environment attenuates the stimulatory effect of endurance swimming on duodenal calcium absorption in rats.
abstract: Endurance swimming is known to increase duodenal calcium absorption in normal rats and bone strength in estrogen-deficient rats. Because the stress resulting from forced training often attenuates the stimulatory effect of exercise, swimming in an inescapable chamber should reveal both the positive effect of the exercise and the negative effect of stress. In the work reported herein, swimming rats showed no signs of stress during 2 weeks of training. However, stress response gradually developed thereafter and peaked at weeks 6 and 7. In rats swimming for 2 weeks, transcellular duodenal calcium transport was enhanced ~2-fold. In contrast, calcium absorption was reduced in rats swimming for 8 weeks, consistent with the absence of swimming-induced upregulation of calcium transporter genes in the 8-week group. In conclusion, prolonged stress hindered the stimulatory effect of swimming on duodenal calcium absorption, and thus endurance exercise should be performed without forced training or stress to retain its beneficial effect on calcium metabolism.
authors.affiliation: Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Bangkok, 10400, Thailand. naratt@narattsys.com
authors.forename: Narattaphol
authors.initials: N
authors.lastname: Charoenphandhu
authors.forename: Jarinthorn
authors.initials: J
authors.lastname: Teerapornpuntakit
authors.forename: Sarawut
authors.initials: S
authors.lastname: Lapmanee
authors.forename: Nitita
authors.initials: N
authors.lastname: Dorkkam
authors.forename: Nateetip
authors.initials: N
authors.lastname: Krishnamra
authors.forename: Jantarima
authors.initials: J
authors.lastname: Charoenphandhu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004386:Duodenum / Q000378:metabolism*; D005260:Female; D007408:Intestinal Absorption / Q000502:physiology; D010805:Physical Conditioning, Animal / Q000502:physiology* / Q000523:psychology; D010807:Physical Endurance / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013312:Stress, Physiological / Q000235:genetics / Q000502:physiology*; D013550:Swimming / Q000502:physiology* / Q000523:psychology
chemical_list: D002118:Calcium