Plasma adrenocorticotropin in domestic geese: effects of ether stress and endocrine manipulations.

A direct radioimmunoassay for the determination of avian adrenocorticotropin (ACTH) in a small volume of plasma was developed using an antiserum specific for N-terminal region of the ACTH molecule. The sensitivity of the two stage assay is 0.1 fmol ACTH/tube. The specificity of the antiserum was tested by its cross reactions with synthetic ACTH fragments and by comparing curves obtained by dilution of different plasma specimens to that of ACTH reference standard. Adrenocorticotropin responses of chronically cannulated geese to ether stress were evaluated and compared to changes of plasma corticosterone (B) concentration over a 2-hr period. ACTH showed a maximum between 5 and 10 min after ether exposure, while B peak appeared 10-15 min later. Thirty minutes after ether inhalation plasma ACTH returned to the baseline, while B response was longer-lasting and decreased to the resting level between 60 and 120 min. Basal and stress-induced ACTH plasma levels were also investigated in male and female gonadectomized and thyroidectomized geese. Castration increased, while thyroidectomy decreased the basal ACTH concentration. These endocrine manipulations did not, however, markedly affect the stress-induced ACTH hypersecretion except in thyroidectomized ganders, where the increment of plasma ACTH 10 min after ether inhalation was significantly lower than in sham operated control geese.