Corticosterone storage within the adrenal cortex: evidence for a sulphate conjugate

Incubation of homogenized rat adrenal glands with sulphatase for 18 h resulted in a significant increase in the amount of unconjugated corticosterone that could be extracted from the gland and which could not be attributed to de-novo synthesis of corticosterone during the incubation. Therefore corticosterone may be stored within the adrenal gland as a sulphate conjugate rather than as unconjugated hormone. Exposure of animals to footshock stress resulted in an increase in the amount of unconjugated corticosterone in the gland and a disappearance of the conjugate form. The rapid disappearance of the sulphate conjugate may reflect the activation of a steroid sulphatase by ACTH. However, the release of corticosterone from a storage form such as corticosterone sulphate could not explain entirely the initial increase in plasma corticosterone concentration following the stress. It was calculated that a pair of adrenal glands would have to store up to 20 nmole corticosterone in order to account for the initial increase in plasma corticosterone. This level was much greater than that extracted from a pair of glands (4.8 nmol) even after sulphatase pretreatment.