AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 2 427-R430, Copyright © 1989 by American Physiological Society
Control of canine ACTH by corticosteroids: an integral feedback effect of steroids
M. Keller-Wood
Department of Pharmacodynamics, University of Florida, Gainesville 32610.
These experiments were designed to test whether the pattern of change in
plasma corticosteroid or the total corticosteroid dose is important in
determining the degree of inhibition of adrenocorticotropic hormone (ACTH)
responses to stress by corticosteroid intermediate-delayed feedback. Five
conscious dogs were studied. The ACTH response to induced hypoglycemia was
measured after no prior corticosteroid feedback signal or after a
corticosteroid feedback signal produced by infusion, two bolus injections,
or three bolus injections of cortisol and corticosterone. The total
corticosteroid dose (45 micrograms/kg) and the total interval of steroid
treatment (60-30 min before hypoglycemia) were the same in all three cases
of corticosteroid treatment. Changes in plasma glucose concentration during
induced hypoglycemia were not altered by corticosteroid treatment. The
plasma ACTH response to hypoglycemia was inhibited by all three patterns of
treatment with corticosteroids. The inhibition of ACTH response was not
significantly altered among the patterns of treatment with corticosteroids.
The data suggest that the integrated (total) or the mean change in plasma
corticosteroid concentration over time determines the degree of inhibition
of stimulated ACTH in this time domain.
