Changes in intestinal galactose and leucine transport during development in the chick: effect of low external calcium

There is some controversy in the literature as to the changes in sugar and amino acid absorption capacity by chicks during intestinal development in the posthatching period. For this reason, the transport of 5mM D-galactose and 4 mM L-leucine was studied in the mild intestine of the developing chick (range: 1 day to 35 days after hatch). In everted sacs, the net transepithelial transport of both substrates was maximal in the 1 to 3 days period and then it declined over the next 4 weeks. The final serosal:mucosal concentration ratio for galactose was 3.58 in 1 to 3-day-old chicks and fell to 1.62 in 26 to 30-day-old birds, while for leucine it fell from 3.52 to 1.50 in the same period. In intestinal rings from 1-day-old chicks, the uptake of 1 mM galactose after 1 min incubation was four times greater than in older animals. When the external calcium concentration was reduced from 2.5 mM (controls) to .1 mM the transport of galactose and leucine was markedly reduced: galactose transport was inhibited by 68 to 57% in 1 to 28-day-old chicks; leucine transport was inhibited by 82 to 50% in 1 to 7-day-old chicks with no significant effect thereafter.