Rat jejunal disaccharidase activity increases biphasically during early post-natal development.

1. Injection of hydrocortisone into 9-day-old rats induces the early appearance of sucrase in jejunal homogenates, the time course of the subsequent increase and magnitude of the final effect being similar to that seen to start on day 16 during normal development. 2. Cytochemical comparison of the effect of hydrocortisone and normal development on the appearance of a mixture of sucrase, maltase, isomaltase and trehalase disaccharidases (alpha-glucosidase activity) shows this enzyme to appear first in enterocytes at the base of the villus. Enzyme activity then increases and spreads along the whole villus during the next 96 h. 3. The rate at which enterocytes migrate along the villus after hydrocortisone injection is not significantly different from that measured during the early phase of normal development. The later phase of normal development is associated with a threefold increase in cell migration rate and a twofold increase in crypt depth. 4. The rate at which alpha-glucosidase activity increases in enterocytes at the base of the villus during early normal development is similar to that determined after hydrocortisone injection into younger animals. This rate of appearance increases eight to tenfold during normal development, shortly after the appearance of solid food in the stomach of normal control animals. 5. Injection of steroid hormones into young rats is generally supposed to mimic events taking place normally at weaning. Present results show alpha-glucosidase induction during normal development to be under more complicated control than had been previously suspected.