Comparison of Plasma Corticotropin Concentration in Intact and Adrenalectomized Dogs and Cats During Hemorrhage

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Abstract
The concentration of ACTH in arterial blood samples from dogs and cats was determined by the adrenal ascorbic acid depletion assay or the plasma corticosterone assay. ACTH was extracted from plasma samples by running acidi-fied plasma through IRC-50 resin columns. The mean recovery of en-dogenous ACTH in the eluate from these columns was 80%. The mean recovery of exogenous ACTH added to dog blood was 91%. The increase in plasma ACTH concentration induced by hemorrhage in dogs and cats at 2 hr. after adrenalectomy was greater than the increase in concentra-tion observed in shamadrenalectomized and intact animals. This marked augmentation of the response to hemorrhage after adrenalectomy sug-gests that the 80-90% decrease in circulating cortlcosteroids known to occur in the 2 hr. after adrenalectomy is sufficient to increase the rate of release of ACTH during stress. Similar results were obtained when adrenal cortical secretion was reduced by the administration of metyra-pone (Su-4885).