Delineation of the glucocorticoid-sensitive period of intestinal development in the rat.
Jejunal sucrase has been used as a marker for intestinal development. The effects of sequential adrenalectomy and sequential administration of hydrocortisone have led to the conclusion that the glucocorticoid sensitivity of the jejunum ceases abruptly at a postnatal age of 17--18 days. Adrenalectomy on day 17 or earlier resulted in significant depression of the usual developmental rise of sucrase activity, whereas adrenalectomy on days 18, 21, or 28 or in adults had no effect on sucrase activity. In contrast, the effect of adrenalectomy on body weight was similar to all ages studied. When hydrocortisone (50 microgram/g BW) was administered to intact animals on day 15 or 16, it caused significant elevation of sucrase activity but, when administered on day 17, 18, or 28, there was no difference between control and treated animals. Since adrenalectomy on day 15 delayed weaning, it was possible that the glucocorticoid dependence of the younger animals was mediated by effects on feeding behavior. However, a further study showed that complete prevention of weaning did not depress sucrase activity between days 15--21. Thus, at early ages, when the tissue was sensitive to glucocorticoid, it was independent of dietary regulation. In contrast, at later ages (days 25 and 27), prevention of weaning caused significant depression of jejunal sucrase activity.