Regulation of 18-oxocortisol and 18-hydroxycortisol by the renin-angiotensin system and ACTH in man.
Based on urinary excretion studies the secretion of the cortisol derivatives, 18-oxocortisol and 18-hydroxycortisol are believed to be regulated by ACTH and to a lesser degree by the renin-angiotensin system. Plasma concentrations of 18-oxocortisol and 18-hydroxycortisol were measured during the simultaneous activation of the renin-angiotensin system and inhibition of ACTH secretion. Five healthy male subjects consuming a sodium diet ad libitum were studied. Blood was drawn at 0800 h after 1 h in the supine position. In the first set of experiments, the subjects remained in the supine position from 0800 to 1000 h with or without the oral administration of 2 mg dexamethasone at 0800 h. In the second set of experiments the subjects were placed in the upright position after drawing the 0800 h sample. The subjects were studied with and without dexamethasone administered at 0800 h. Blood was drawn again at 1000 h. Plasma levels of 18-oxocortisol, 18-hydroxycortisol, ACTH, plasma renin activity (PRA), cortisol, aldosterone and 18-hydroxycorticosterone were measured by radioimmunoassay. None of these parameters changed during the 2 h in the supine position. 18-Oxocortisol, 18-hydroxycortisol, aldosterone, 18-hydroxycorticosterone and PRA increased, but ACTH and cortisol did not change when the subjects were placed in the upright position. After dexamethasone administration, 18-oxocortisol, 18-hydroxycortisol, cortisol, aldosterone and 18-hydroxycorticosterone decreased in the supine position and no increase occurred in 18-oxocortisol, 18-hydroxycortisol and 18-hydroxycorticosterone in the upright position. PRA and aldosterone increased and ACTH and cortisol decreased in these subjects. 18-Oxocortisol and 18-hydroxycortisol were more dependent on ACTH regulation and less on the renin-angiotensin system than aldosterone.
Yamakita
N
N
Institute of Clinical Medicine, University of Tsukuba, Tsukuba-City, Japan.
Gomez-Sanchez
C E
CE
Mune
T
T
Yoshida
H
H
Miyazaki
S
S
Yasuda
K
K
Nakai
T
T
D015069:18-Hydroxycorticosterone / Q000097:blood; D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000502:physiology*; D000328:Adult; D000450:Aldosterone / Q000097:blood; D003907:Dexamethasone / Q000008:administration & dosage / Q000494:pharmacology; D004032:Diet; D006801:Humans; D006854:Hydrocortisone / Q000031:analogs & derivatives* / Q000097:blood; D007564:Japan; D008297:Male; D011187:Posture; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System / Q000502:physiology; D012964:Sodium / Q000494:pharmacology
C038135:18-oxocortisol; D000450:Aldosterone; D015069:18-Hydroxycorticosterone; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D012964:Sodium; D012083:Renin; C033689:18-hydroxycortisol; D006854:Hydrocortisone