The effect of hydrocortisone on exportable enzyme accumulation in the differentiating chick pancreas

Developmental patterns of accumulation of chymotrypsinogen, procarboxypeptidase A, amylase, and endonuclease in the embryonic chick pancreas were compared. The enzymes studied seem to fall into two classes: (1) those, like amylase and procarboxypeptidase, which start to accumulate rapidly at early stages of development and which accumulate in two steps; and (2) those, like chymotrypsinogen and endonuclease, which accumulate slowly during early development (before 14 days) and rapidly thereafter in a single step. Hydrocortisone (hemisuccinate) injection at 10 and 12 days of development causes a precocious increase in the levels of amylase, procarboxypeptidase A, chymotrypsinogen, and, to a lesser extent, endonuclease. The levels of chymotrypsinogen and endonuclease increase during the first day after hydrocortisone injection, whereas the levels of amylase and procarboxypeptidase A are elevated only after a lag of at least a day. Effects of hydrocortisone injection on acinar cell ultrastructure were also investigated. Injection of the hormone prematurely induced a rapid proliferation of the rough endoplasmic reticulum and a sharp increase in the number and size of zymogen granules. The data support the hypothesis that the exocrine chick pancreas differentiates in two phases, an early phase and a maturation phase and that the latter phase is initiated by adrenal cortical steroids secreted by the embryo.