Patterns of growth and α-amylase activity in the developing chick pancreas

1. 1. Developmental changes in total pancreatic protein, DNA, RNA and α-amylase (α-1,4-glucan 4-glucanohydrolase, EC 3.2.1.1) activity were studied in chick embryos aged 10-20 days and in 1-5-day-old chicks (developmental age 21-25 days). 2. 2. The protein content of the pancreas increases rapidly from 10 to 13 days, more slowly from 13 to 18 days, very rapidly from 19 to 22 days and again more slowly from 22 to 25 days. 3. 3. A virtually constant concentration of RNA per mg of protein is observed from 13 to 25 days of development. On the other hand, the concentration of DNA per mg of protein, which is constant from 13 to 18 days, falls sharply between 18 and 21 days. 4. 4. The specific activity of amylase remains constant from 11 to 16 days of development and increases about 8-fold from 16 to 22 days, after which it falls. At its maximum concentration (22-23 days) amylase constitutes about 12% of the total pancreatic protein. 5. 5. It seems significant that the steepest rise in amylase activity between 18 and 22 days coincides with the period of rapid growth and increase in cell size which overlaps the time of hatching.