Abstract

In dogs, the administration of dexamethasone induced adrenocortical suppression as evidenced, 72 hours after withdrawal of steroid, by failure of a normal elevation in plasma unconjugated 17-hydroxycorticosteroid (17-OHCS) levels following the intravenous infusion of ACTH, or the application of a standard surgical trauma. Such suppressed animals, however, were as capable of coping with the stress of surgical trauma under ganglionic blockade or a profound 30-minute hemorrhagic hypotension as control animals, although the latter exhibited a much greater capacity for increasing their adrenal output of 17-OHCS under the conditions described. Hemodynamics and responsiveness to the sympathomimetic amine, levarterenol, have remained comparable for both control and suppressed groups.

The high endogenous steroid levels usually observed in control animals following the stresses imposed, appear to be much in excess of some unknown minimal quantity necessary at least for circulatory homeostasis in the dog. The findings are not in accord with the concept that large amounts of glucocorticoids are required to obtain a full response to a large stress.

Certain possibilities to account for the results obtained are considered.