Immunoneutralization of corticotropin-releasing hormone prevents the diurnal surge of ACTH.
To determine whether CRH is required for the evening rise in plasma ACTH, rats were injected at 0800 hr with CRH antiserum (anti-CRH) or normal rabbit serum (NRS). Blood samples were taken through venous catheters at 0800 hr before treatment and at 1300, 1700, and 2100 hr. Plasma was assayed for immunoreactive ACTH and corticosterone. There was no significant difference in pretreatment values between the two groups. Immunoneutralization of CRH abolished the rise in plasma ACTH seen at 1700 hr in the NRS group but had little effect on earlier levels. The diurnal elevation in plasma corticosterone continued after anti-CRH treatment, but peak levels occurred earlier. Plasma ACTH and corticosterone were significantly correlated at the time of the diurnal surge, but not at 0800 hr or 1300 hr in the NRS controls or at any time point in the anti-CRH group. These results suggest that CRH is required for the diurnal surge of plasma ACTH. They also confirm previous observations by others that the adrenal cortex does not require active CRH or a diurnal surge of ACTH in order to exhibit a significant diurnal increase in secretion of corticosterone, and that factors other than CRH may be relatively more active than CRH in regulation of ACTH secretion during the time of circadian inactivity.
Carnes
M
M
Geriatrics Section, Wm. S. Middleton Memorial Veterans Hospital, Madison, WI 53705.
Lent
S J
SJ
Erisman
S
S
Barksdale
C
C
Feyzi
J
J
D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000276:immunology / Q000502:physiology*; D007106:Immune Sera / Q000494:pharmacology; D008297:Male; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains
D007106:Immune Sera; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone