Independence of salt gland function and adrenocortical activity in ducks (Anas platyrhynchos)

In immature ducklings injected with hypertonic saline the volume of extrarenal salt gland secretion was unaffected by prior treatment (immediately or 4 hr before salt loading) with long-lasting adrenocorticotrophin (ACTH 100 iu/kg, im) or exogenous corticosterone (1.0 mg/kg, im). Pretreatment with metyrapone, an 11-beta-hydroxylase blocker, (80 mg/kg, im) 4 hr before salt loading did not effect the volume of salt gland secretion but delayed the onset of extrarenal excretion. Salt gland function was suppressed in birds pretreated with metyrapone immediately prior to salt loading. The intravenous administration of metyrapone after salt loading immediately reduced salt gland activity, which remained suppressed for at least 40-50 min thereafter. The inhibitory effect of metyrapone on salt gland activity was not counteracted by the subsequent or simultaneous administration of exogenous corticosterone to salt-loaded ducks. These results suggest that acute alterations in adrenocortical activity are not causally responsible for changes in salt gland function.