Abstract:
Endurance impact exercise, such as running, is known to improve calcium
metabolism in humans and rats, in part, by stimulating intestinal calcium absorption,
whereas immobilization induces a decrease in intestinal calcium absorption.
However, the effect of non-impact exercise, such as swimming, on intestinal
calcium absorption is controversial. This study thus aimed to investigate the effect
of endurance swimming on calcium absorption in the duodenum, proximal jejunum,
distal jejunum, ileum, cecum, proximal colon, and distal colon of female Sprague-
Dawley rats. The animals were divided into 2-, 4-, 6-, and 8-week swimming
groups and age-matched sedentary controls. Intestinal segments were mounted in
modified Ussing chambers for measurement of the transepithelial calcium fluxes.
Electrical parameters were measured by a computer-assisted clamping setup.
Epithelial charge selectivity was determined by the dilution potential technique.
The results showed that endurance swimming for 2 weeks significantly
increased calcium absorption in the duodenum, proximal jejunum and cecum. In
contrast, the total active calcium absorption was decreased in the proximal colon,
while having no effect on the distal jejunum, ileum, and distal colon. In the
duodenum, 2-week swimming led to an increase in calcium transport through the
transcellular active mechanism, but not the solvent drag-induced mechanism. The
paracellular passive calcium transport, calcium permeability, and epithelial chargeselective
property were also not altered. On the other hand, duodenal calcium
absorption was not changed after 4- and 6-week swimming, and was decreased after
8-week swimming.
It could be concluded that short-term swimming (2 weeks), but not long-term
swimming (4−8 weeks) enhances the intestinal calcium absorption via the
transcellular pathway. The responses to endurance swimming mostly occurred in
the intestinal segments which possessed transcellular active transport mechanisms,
i.e., duodenum, proximal jejunum, and cecum.