Effects of ovarian steroid hormones and thyroxine on calcitonin
secretion in pregnant rats.
Lu, Chien-Chen, Shiow-Chwen Tsai, Shyi-Wu Wang, Ching-Lin Tsai, Chin
-Pang Lau, Hsi-Chang Shih, Yen-Hao Chen, Yu-Chung Chiao, Charlie Liaw,
and Paulus S. Wang.
Department of Physiology, School of Life Science, National Yang
-Ming University, and Department of Orthopaedic Surgery, School of
Medicine, National Taiwan University, Taipei, and Department of
Physiology, Chang-Gung University, Tao-Yuan, Taiwan, Republic of
China
APStracts 4:0240E, 1997.
In the present study, the roles of ovarian steroid hormones and
thyroxine (T4) in regulating the secretion of calcitonin (CT) in
pregnant rats were examined. The levels of plasma progesterone, pre-
and post-CaCl2 plasma CT, and recovery time of plasma CT and calcium
after calcium challenge were greatest in midterm pregnant rats. The
levels of basal plasma progesterone, CT, calcium and recovery time of
plasma CT after calcium challenge were less in late pregnant rats,
but basal plasma estradiol was highest in late pregnancy. The
concentrations of plasma T4 were gradually decreased in rats during
pregnancy. Regardless of the presence of estradiol, administration of
progesterone in ovariectomized (Ovx) rats resulted in an increase of
plasma T4 as well as the basal and calcium-induced secretion of CT.
Administration of estradiol alone did not alter the CaCl2-induced
levels but decreased the post-CaCl2 levels of plasma calcium in Ovx
rats. The basal levels of plasma CT were decreased in Ovx rats
treated with T4. These results suggest that the hypercalcitoninemia
in midterm pregnant rats is due to an increased secretion of
progesterone. Hypocalcitoninemia in late pregnant rats, however, is
due in part to lower plasma calcium.
Received 19 May 1997; accepted in final form 29 October 1997.
APS Manuscript Number E225-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 14 November 1997