The regulation of bioactive and immunoreactive acth secretion by
crf and avp in sheep fetuses at 0.70 and 0.90 gestation.
Zehnder, Timothy J., Nancy K. Valego, Jeffrey Schwartz, Anne White,
and James C. Rose.
Department and Institution, Departments of Physiology and
Pharmacology and Obstetrics and Gynecology and Perinatal Research
Laboratories, Bowman Gray School of Medicine, Wake Forest University,
Winston-Salem, NC 27157-1066 Endocrine Sciences Research Group,
University of Manchester, Manchester, UK
APStracts 2:0151E, 1995.
The purpose of this study was to determine the effects of CRF or AVP
on the secretion of bioactive ACTH (B-ACTH) and immunoreactive ACTH;
the latter being measured by RIA ("I-ACTH")and separate two
-site immunoradiometric assays for ACTH(1-39) and ACTH precursors.
Experiments were performed on chronically catheterized fetal sheep at
0.70(n=9) and 0.90(n=8) gestation. Each fetus received a 15min
infusion of CRF, AVP, or saline on 3 consecutive days. Blood was
obtained before(0), 15min(15), and 60min after(60) the infusion
began. Results were analyzed by ANOVA and independent t-tests, and
are presented as means+/-SEM. Significant differences were accepted
when p < 0.05. CRF significantly increased I-ACTH at 15
(younger) and 60min (both groups). CRF significantly increased B-ACTH
and the B/I ACTH ratio in both groups at 15 and 60min. AVP
significantly increased I-ACTH, B-ACTH and the B/I ACTH ratio in both
groups at 15min. In two subgroups (n=4/subgroup), CRF significantly
increased ACTH(1-39) and ACTH precursors at 15 and 60min. CRF
increased the ratio of ACTH(1-39)/ACTH precursors at 15 (younger) and
60min (both groups). AVP increased ACTH(1-39), ACTH precursors, and
the ratio of ACTH(1-39)/ACTH precursors in both groups at 15 min.
These findings show that both CRF and AVP can stimulate the secretion
of B-ACTH, ACTH(1-39), and ACTH precursors at 0.70 and 0.90
gestation. The proportional increments in B-ACTH/I-ACTH and ACTH(1
-39)/ACTH precursors suggest that CRF and AVP evoke selective
increases in B-ACTH and ACTH(1-39).
Received 4 April 1995; accepted in final form 10 July 1995.
APS Manuscript Number E159-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.