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Adrenocortical function in the duck (Anas platyrhynchos) Donaldson, Edward Mossop

Abstract

18-hydroxycorticosterone, aldosterone and corticosterone were positively characterized in duck adrenal incubates. A compound resembling 11-dehydrocorticosterone was also present. The addition of 1 I.U. of ACTH/100 mg of adrenal tissue caused an increase in the production rate of all four steroids. The most dramatic effect however, was observed with respect to the synthesis of corticosterone. Aldosterone-4-¹⁴C and 18-hydroxycorticosterone-4-¹⁴C were isolated from the media of adrenal glands incubated in the presence of a tracer amount of corticosterone-4-¹⁴C. During the incubation the maximum specific activity recorded for aldosterone-4-¹⁴C was 66% of the specific activity of the precursor. This observation indicated that the primary pathway to aldosterone in the duck adrenal was probably via corticosterone. 18-hydroxycorticosterone may be an intermediate between corticosterone and aldosterone or may be a distinct end product of unknown biological activity. No difference in the biological half-life (T₁/2) of corticosterone was found between fresh-water maintained fresh-water loaded birds and birds maintained on fresh water or saline and loaded with saline. An increase in the apparent volume of distribution (A.V.D.) of corticosterone was found however in saline loaded ducks. This resulted in an increased secretory rate of corticosterone in those animals loaded with saline. In the saline maintained ducks an increased adrenal size was responsible for the enhanced corticosterone secretory rate. In those ducks maintained on fresh water and loaded with saline a weight specific increase in the corticosterone secretory rate was apparent. The implications of the increased corticosterone secretory rate are discussed in relation to the known dependence of nasal gland function in marine birds on a functional adrenal cortex.

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