Related Experiment Videos
Maturation of calcium transport in the rat small and large intestine
Insights
Calcium transport in rat intestines changes significantly from infancy to adolescence. Weaning shifts calcium absorption from passive to carrier-mediated mechanisms, impacting overall intestinal calcium uptake.
Area of Science:
- Physiology
- Gastroenterology
- Developmental Biology
Background:
- Intestinal calcium absorption is crucial for development and bone health.
- Understanding age-related changes in calcium transport mechanisms is vital for pediatric nutrition and health.
Purpose of the Study:
- To investigate age-dependent alterations in calcium transport across different segments of the rat intestine.
- To determine how calcium (Ca) transport mechanisms evolve from suckling to adolescent stages.
Main Methods:
- In vivo perfusion technique used to assess calcium transport rates in proximal and distal small intestine, and colon of rats at different ages (2, 3, and 6 weeks).
- Luminal calcium concentrations were varied below and above physiological levels to analyze transport kinetics.
Main Results:
- Suckling rats exhibited linear calcium transport, with net secretion at low concentrations and net absorption at high concentrations.
- Weanling rats showed curvilinear transport across all segments, indicating a shift in mechanism.
- Adolescent rats displayed curvilinear transport in the proximal intestine and linear transport in the distal intestine and colon.
- Calcium transport rates were substantially higher in suckling rats compared to adolescent rats.
Conclusions:
- The mode of intestinal calcium transport shifts from predominantly passive in suckling rats to primarily carrier-mediated in adolescent rats.
- Weaning represents a critical period for the maturation of intestinal calcium absorption pathways.
Abstract:
Using an in vivo perfusion technique we compared transport of calcium in segments of the proximal (duodenum + jejunum) and distal (ileum) small intestine and in the cecum + colon of suckling (2-week old), weanling (3-week-old) and adolescent (6-week-old) rats. The concentration of calcium (Ca) in the isotonic sodium chloride solution perfused through the intestinal segments was either below (0.4 and 1.4 mmoles/1) or above (3.2 mmoles/1) serum ionized calcium. In the suckling rat, in all three intestinal segments, the relationship between transport rate (mumoles/hr per g wet weight) and luminal Ca concentration was linear. Net secretion occurred when luminal Ca concentration was below serum ionized Ca, and net absorption at 3.2 mmoles/l luminal Ca. In the weanling rats the relationship between luminal Ca concentration and transport rate was curvilinear for all segments. In the adolescent rats the relationship was curvilinear in the proximal segment and linear in the distal segment and in the cecum + colon. Rates of transport in segments of the suckling rats were several fold greater than corresponding rates in the adolescent rats. The change in the relationship between transport rate and luminal Ca suggested that the mode of transport of Ca changes at the time of weaning from mainly a passive mechanism in the suckling period to mainly a carrier mediated mechanism in the adolescent rats.