SEQUENTIAL CHANGES IN RAT THYMUS AFTER THE SUBCUTANEOUS INJECTION OF CORTISOL

Abstract

SUMMARY Several properties of the thymus were examined from the point of view of the mechanism of corticosteroid-induced involution. Involution, as measured by weight loss, proceeded for 3 days after a single subcutaneous injection of cortisol (3·0 mg./100 g. body wt.) into male rats. In thymus slices there was initially a transient inhibition of oxygen uptake. Other changes, namely a decreased concentration of ribonucleic acid and an increased release of protein from incubated slices, occurred later. There was no change in the degree of penetration of inulin, sucrose or sodium into incubated slices. It is thought that the results are consistent with the concept that cortisol sets in motion a set sequence of events, and that some of the changes are not dependent on the continued presence of hormone in the gland.