The effect of an anti-glucocorticoid (ZK 98299) on thymus evolution and on hydrocortisone-induced thymolysis, intestinal brush-border enzymes and their desialylation in suckling rats.

1. The action in Onapristone infant male rats displays short-term and delayed effects. 2. Suppression of intestinal brush-border enzymes and increase of thymus mass were observed only immediately after 3-day treatment with Onapristone. After an additional 3 days its effect disappeared. There was no immediate or delayed effect of Onapristone on the desialylation of brush-border enzymes. 3. In the short-term and delayed effects, Onapristone suppressed the HC-provoked induction of several intestinal brush-border enzymes, especially alpha-glycosidases. In the delayed effect the drug also suppressed thymolysis induced by the exogeneously given glucocorticoid, and suppressed the HC-induced desialylation of a brush-border enzyme DP IV, which serves as a marker of the desialylation process. 4. These experiments seem to support a conclusion that the postnatal development of intestinal brush-border enzymes and the development of thymus in infant rats are controlled by endogeneously secreted glucocorticoids. 5. The control of sialylation of intestinal brush-border proteins by endogeneously secreted glucocorticoids during the postnatal development of the rat remains debatable.