Endocrinology, Vol 126, 3179-3184, Copyright © 1990 by Endocrine Society

ARTICLES

Acute stimulation of prolactin release by estradiol: mediation by the posterior pituitary

I Murai and N Ben-Jonathan
Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46223.

We have previously shown that the posterior pituitary contains a potent PRL-releasing factor (PRF). Estradiol stimulates PRL release by acting at three possible sites: the hypothalamus, the anterior pituitary, and the posterior pituitary. The objectives were 1) to document the profiles of PRL and LH release in response to an acute administration of estradiol, and 2) to identify the site of action of estradiol by employing two surgical approaches, pituitary stalk section (SS) and posterior pituitary lobectomy (LOBEX). Ovariectomized rats were used throughout. In Exp 1, rats were injected iv with 5 micrograms/kg 17 beta-estradiol, and blood was collected at 30-min intervals for 4 h. Estradiol induced a rapid and profound decline in plasma LH levels and a delayed, 5- to 6-fold rise in PRL. The purpose of the second experiment was to determine whether estradiol stimulates PRL release by acting at the anterior pituitary. Injection of estradiol to SS rats failed to stimulate a rise in PRL. We have previously reported that lactotrophs of SS rats are responsive to PRL secretagogues such as TRH. The objective of the third experiment was to differentiate between hypothalamic and posterior pituitary sites of estradiol action. Estradiol induced only a small rise in PRL when injected into LOBEX rats. However, LOBEX and control rats showed similar large rises in PRL in response to injection of alpha-methyl-para-tyrosine, an inhibitor of tyrosine hydroxylase. The latter indicates that the hypothalamic dopaminergic system as well as anterior pituitary lactotrophs are functionally intact in LOBEX rats. We conclude that estradiol administration to ovariectomized rats induces a rapid decline in LH and a delayed marked increase in PRL. The posterior pituitary, probably via PRF, is the primary site that mediates the acute effects of estradiol on PRL release. Estradiol does not stimulate PRL release directly from the anterior pituitary. The role of the hypothalamus is unclear. Estradiol could act directly on PRF-containing cells in the posterior pituitary or indirectly, via hypothalamic neurons terminating in the posterior pituitary. The hypothalamus also has a minor component that responds to estradiol and is independent of the posterior pituitary.

This article has been cited by other articles:

				P W Harvey, D J Everett, and C J Springall Hyperprolactinaemia as an adverse effect in regulatory and clinical toxicology: role in breast and prostate cancer Human and Experimental Toxicology, July 1, 2006; 25(7): 395 - 404. [Abstract] [PDF]

				C. Lin Chang, J. Roh, J.-I. Park, C. Klein, N. Cushman, R. V. Haberberger, and S. Y. T. Hsu Intermedin Functions as a Pituitary Paracrine Factor Regulating Prolactin Release Mol. Endocrinol., November 1, 2005; 19(11): 2824 - 2838. [Abstract] [Full Text] [PDF]

				C. J. Thompson, N. N. C. Tam, J. M. Joyce, I. Leav, and S.-m. Ho Gene Expression Profiling of Testosterone and Estradiol-17{beta}-Induced Prostatic Dysplasia in Noble Rats and Response to the Antiestrogen ICI 182,780 Endocrinology, June 1, 2002; 143(6): 2093 - 2105. [Abstract] [Full Text] [PDF]

				E. Nishihara, Y. Nagayama, S. Inoue, H. Hiroi, M. Muramatsu, S. Yamashita, and T. Koji Ontogenetic Changes in the Expression of Estrogen Receptor {alpha} and {beta} in Rat Pituitary Gland Detected by Immunohistochemistry Endocrinology, February 1, 2000; 141(2): 615 - 620. [Abstract] [Full Text] [PDF]

				M. E. Wilson, R. H. Price Jr., and R. J. Handa Estrogen Receptor-{beta} Messenger Ribonucleic Acid Expression in the Pituitary Gland Endocrinology, December 1, 1998; 139(12): 5151 - 5156. [Abstract] [Full Text] [PDF]

				D. J. Tortonese, J. Brooks, P. M. Ingleton, and A. S. McNeilly Detection of Prolactin Receptor Gene Expression in the Sheep Pituitary Gland and Visualization of the Specific Translation of the Signal in Gonadotrophs Endocrinology, December 1, 1998; 139(12): 5215 - 5223. [Abstract] [Full Text] [PDF]

				N. A. Mitchner, C. Garlick, and N. Ben-Jonathan Cellular Distribution and Gene Regulation of Estrogen Receptors {alpha} and {beta} in the Rat Pituitary Gland Endocrinology, September 1, 1998; 139(9): 3976 - 3983. [Abstract] [Full Text] [PDF]

				R. Hnasko, S. Khurana, N. Shackleford, R. Steinmetz, M. J. Low, and N. Ben-Jonathan Two Distinct Pituitary Cell Lines from Mouse Intermediate Lobe Tumors: A Cell that Produces Prolactin-Regulating Factor and a Melanotroph Endocrinology, December 1, 1997; 138(12): 5589 - 5596. [Abstract] [Full Text] [PDF]

				R. Steinmetz, N. G. Brown, D. L. Allen, R. M. Bigsby, and N. Ben-Jonathan The Environmental Estrogen Bisphenol A Stimulates Prolactin Release in Vitro and in Vivo Endocrinology, May 1, 1997; 138(5): 1780 - 1786. [Abstract] [Full Text] [PDF]

				D. L. Allen, N. A. Mitchner, T. E. Uveges, K. P. Nephew, S. Khan, and N. B. Jonathan Cell-Specific Induction of c-fos Expression in the Pituitary Gland by Estrogen Endocrinology, May 1, 1997; 138(5): 2128 - 2135. [Abstract] [Full Text]