Endocrine Influences on the Functional Differentiation of the Small Intestine

Publisher Website
Google Scholar
Abstract
The epithelium of the small intestine achieves a state of functional differentiation during fetal life, later redifferentiating in keeping with the changing needs of the developing animal. These events and their hormonal control have been most intensively investigated in rats and mice, in which the first phase of differentiation occurs during the last 2 to 3 days in utero. In newborn animals the duodenal epithelium transports intact immunoglobulins into the circulation, that of the ileum digests milk constituents engulfed by pinocytosis. Except for lactase, the brush border of the ileum is poorly furnished with enzymes associated with the border in adults. Conversion to the mature state occurs within 3 to 4 days during the third postnatal week. Experiments on intact sucklings or those derived of hypophysis, adrenal, or thyroid glands show that epithelial maturation depends on adequate titers of corticosteroids and thyroxine, with either hormone eliciting nearly normal redifferentiation in the absence of the other. Evidence indicates that the intestine in utero is responsive to the same hormones. In animals with long gestation periods fragmentary evidence reveals that an advanced degree of differentiation, including high activity of some intracellular and brush border enzymes, may be attained weeks or months before birth. Pinocytosis of ingested or desquamated materials occurs during intrauterine life. Lactase, which is essential for the digestion of milk, appears during the perinatal period, probably under the influence of high titers of thyroid hormones or corticosteroids which occur at this time. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.

This publication has 0 references indexed in Scilit: