Endocrinology, Vol 131, 105-113, Copyright © 1992 by Endocrine Society

ARTICLES

A trophoblast-specific factor(s) suppresses circulating prolactin levels and increases tyrosine hydroxylase activity in tuberoinfundibular dopaminergic neurons

LA Arbogast, MJ Soares, H Tomogane and JL Voogt
Department of Physiology, University of Kansas Medical Center, Kansas City 66160-7401.

Rat choriocarcinoma (Rcho) cells, which are morphologically similar to trophoblast giant cells of the normal placenta and produce placental lactogen-I in vivo, were used to investigate placental feedback on PRL secretion and tuberoinfundibular dopaminergic neuronal activity. Rcho cells were injected into female rats either intracerebroventricularly 60-65 h before use or under the kidney capsule 10-14 days before use. The following endocrine conditions were used: 1) ovariectomized rats with or without bromocriptine treatment, 2) immature (40-44 days old) rats, 3) adult cycling (diestrous) rats, and 4) pregnant rats. Serum PRL levels in ovariectomized, diestrous, and immature female rats were suppressed to less than 20% of control levels by secretions from the Rcho cells. Tyrosine hydroxylase (TH) activity in the stalk-median eminence (SME) was increased 2-fold above control activity in Rcho- treated ovariectomized and immature female rats. When TH activity was reduced to 40% of control levels by 50 h of bromocriptine treatment, secretions from Rcho cells increased TH activity 3.5-fold to levels similar to those for Rcho alone. Even though Rcho treatment suppressed PRL levels, TH activity in the SME of cycling (diestrous) rats was not altered after either central (65 h) or peripheral (12 days) administration of cells. TH mRNA levels in the arcuate nuclei were unaltered by Rcho cells in immature female and adult cycling rats. TH mRNA levels in ovariectomized rats were markedly reduced 75% by 50 h of bromocriptine treatment and modestly reduced 33% 65 h after injection of Rcho cells. However, Rcho cells partially reversed the bromocriptine- induced decline in TH mRNA to levels seen for Rcho cells alone. On day 7 of pregnancy, secretions from Rcho cells abolished the nocturnal and diurnal PRL surges characteristic of early pregnancy and suppressed circulating PRL levels throughout the day to less than 20% of intersurge PRL levels. Rcho cells eliminated the semicircadian rhythm in TH activity in the SME, which was out of phase with the twice daily PRL surges of early pregnancy. TH activity was increased by Rcho factor(s) at 0330 h (nocturnal surge) and 1800 h (diurnal surge), but not at 1000 h (intersurge). MMQ cells, pituitary-derived clonal PRL- secreting cells, similarly terminated the biphasic rhythm of PRL release and tuberoinfundibular dopaminergic neuronal activity during early pregnancy.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				F. J. Steyn, G. M. Anderson, and D. R. Grattan Hormonal Regulation of Suppressors of Cytokine Signaling (SOCS) Messenger Ribonucleic Acid in the Arcuate Nucleus during Late Pregnancy Endocrinology, June 1, 2008; 149(6): 3206 - 3214. [Abstract] [Full Text] [PDF]

				G. M. Anderson, P. Beijer, A. S. Bang, M. A. Fenwick, S. J. Bunn, and D. R. Grattan Suppression of Prolactin-Induced Signal Transducer and Activator of Transcription 5b Signaling and Induction of Suppressors of Cytokine Signaling Messenger Ribonucleic Acid in the Hypothalamic Arcuate Nucleus of the Rat during Late Pregnancy and Lactation Endocrinology, October 1, 2006; 147(10): 4996 - 5005. [Abstract] [Full Text] [PDF]

				R. Bertram, M. Egli, N. Toporikova, and M. E. Freeman A mathematical model for the mating-induced prolactin rhythm of female rats Am J Physiol Endocrinol Metab, March 1, 2006; 290(3): E573 - E582. [Abstract] [Full Text] [PDF]

				Z. B. Andrews, I. C. Kokay, and D. R. Grattan Dissociation of Prolactin Secretion from Tuberoinfundibular Dopamine Activity in Late Pregnant Rats Endocrinology, June 1, 2001; 142(6): 2719 - 2724. [Abstract] [Full Text] [PDF]

				M. E. Freeman, B. Kanyicska, A. Lerant, and G. Nagy Prolactin: Structure, Function, and Regulation of Secretion Physiol Rev, October 1, 2000; 80(4): 1523 - 1631. [Abstract] [Full Text] [PDF]

				Y. Lee and J. L. Voogt Feedback Effects of Placental Lactogens on Prolactin Levels and Fos-Related Antigen Immunoreactivity of Tuberoinfundibular Dopaminergic Neurons in the Arcuate Nucleus during Pregnancy in the Rat Endocrinology, May 1, 1999; 140(5): 2159 - 2166. [Abstract] [Full Text]