Development of Na+ transport in the chicken colon.

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.