Adrenal corticosteroid secretion in fetal sheep: pulsatile pattern at rest.
This study was undertaken to define the resting pattern of fetal pituitary-adrenocortical function. Experiments were performed at 127-145 days gestation in fetal sheep with chronic peripheral and adrenal cannulas inserted under halothane anesthesia. With the fetus in a baseline state, over 6 h, at 30-min intervals, maternal and fetal peripheral samples were collected for blood gases and cortisol (F), corticosterone (B), and adrenocorticotropic hormone (ACTH) concentrations, and three successive, 2-min adrenal samples were collected for determination of F and B secretion rates. We observed high-frequency, episodic bursts of F secretion. A lower frequency oscillation of F secretion, with a period of approximately 90 min, was defined by cosinor analysis. The mean amplitude of the oscillation increased from 45 to 507 ng/min with advancing gestation. The pattern of B secretion was similar to that for F but was quantitatively lower. An oscillatory period of approximately 90 min for plasma F was present in a majority of experiments. Pulsatile rhythms for ACTH were defined in 10 of 14 experiments, with periods ranging from 1.64 h in the least mature group to 2.37 h in the oldest fetus. Mean data revealed exponential increases in both F secretion and plasma ACTH from 129 to 145 days gestation.
Jackson
B T
BT
Department of Surgery, Brown University, Providence, Rhode Island.
Lee
A F
AF
Morrison
S H
SH
Baker
R M
RM
Cohn
H E
HE
Piasecki
G J
GJ
D000204:Activity Cycles; D000305:Adrenal Cortex Hormones / Q000378:metabolism*; D000311:Adrenal Glands / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D003345:Corticosterone / Q000097:blood; D005333:Fetus / Q000378:metabolism*; D005865:Gestational Age; D006854:Hydrocortisone / Q000097:blood; D011673:Pulsatile Flow; D012146:Rest; D012756:Sheep
D000305:Adrenal Cortex Hormones; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone; D006854:Hydrocortisone