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Development of Na+ transport in the chicken colon
1Institute of Physiology, Czech Academy of Sciences, Prague.
Insights
Chicken colon Na+ transport develops significantly after hatching, especially on low-salt diets. High salt intake inhibits this crucial sodium absorption adaptation in young chicks.
Area of Science:
- Physiology
- Developmental Biology
- Gastroenterology
Background:
- Colonic sodium (Na+) transport is vital for fluid balance.
- Developmental changes in intestinal ion transport are critical for adaptation after birth.
- Understanding these changes is key to pediatric and comparative physiology.
Purpose of the Study:
- To investigate developmental changes in chicken colon Na+ transport.
- To assess the impact of salt intake on Na+ absorption and Na+, K+-ATPase activity.
- To explore the role of amiloride sensitivity in developmental Na+ transport.
Main Methods:
- Measured amiloride-sensitive short-circuit current (a marker for electrogenic Na+ transport) in chicken embryos and chicks.
- Assessed Na+, K+-ATPase activity in colon tissue.
- Varied dietary salt intake (low-salt vs. high-salt 0.9% NaCl).
Main Results:
- Amiloride-sensitive Na+ transport was absent in embryos but increased post-hatching, particularly on a low-salt diet.
- High salt intake (0.9% NaCl) completely prevented the development of amiloride-sensitive Na+ transport.
- Na+, K+-ATPase activity increased with development but was unaffected by salt intake.
- Amiloride-sensitive Na+ transport showed a gradual increase for at least 15 days post-hatching.
Conclusions:
- Chicken colonic Na+ transport undergoes significant developmental changes.
- Low-salt diet promotes the maturation of electrogenic Na+ absorption in the colon.
- These adaptations are crucial for maintaining sodium balance during early life, with potential aldosterone involvement.
Abstract:
To evaluate the developmental changes in colonic Na+ transport, Na, K-ATPase activity and the sensitivity of the short-circuit current to amiloride were investigated. The amiloride-sensitive short-circuit current which represents the electrogenic, amiloride-sensitive Na+ transport through Na+ channels, was not present in chicken embryos but rose significantly after hatching in chicks which were kept on a low-salt diet. Amiloride-sensitive short-circuit current increased gradually but the plateau was not reached during the first 15 days of life. Drinking of 0.9% NaCl totally inhibited the induction of amiloride-sensitive Na+ transport. Na+, K(+)-ATPase activity increased during development but was not influenced by changes in salt intake. Na+ transport in chicken colon therefore undergoes profound developmental changes. The increase of Na+ transport reflects not only the adaptation of colonocytes to low salt intake but also the maturation of Na+ absorption in colon. The possible role of aldosterone in the adaptation to low-salt intake is discussed.