Circadian alterations in prolactin, corticosterone, and thyroid hormone levels and down-regulation of prolactin receptor activity by 2,3,7,8-tetrachlorodibenzo-p-dioxin |
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| Authors: | M K Jones W P Weisenburger I G Sipes D H Russell |
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| Institution: | 1. Department of Cardiology, St Vincent''s Hospital Melbourne, Australia;2. Mercy Hospital for Women, Heidelberg, Melbourne, Australia;3. Department of Anaesthesia, Northern Health Melbourne, Australia;2. Department of Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine, 676 N Saint Clair, Suite 1000, Chicago, IL, 60611, USA;3. Institute for Juvenile Research, Department of Psychiatry, University of Illinois at Chicago, 1747 West Roosevelt Road, Chicago, IL 60608, USA;4. Department of Psychology, University of Arizona, 1503 E University Blvd., P.O.Box 210068, Tucson, AZ 85721, USA;5. Section on Development and Affective Neuroscience, NIMH Intramural Research Program, 15K North Drive, MSC-2670, Bethesda, MD 20892-2670, USA;6. Department of Medicine, University of Chicago, 900 E. 57th St, Chicago, IL 60637, USA;7. Department of Psychology, Northwestern University, Swift Hall 102, 2029 Sheridan Road, Evanston, IL60208, USA;8. Department of Psychiatry, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85721, USA;9. Office for Research & Economic Development, University of Nebraska-Lincoln, USA;10. Laboratory of Neurogenetics, NIAAA Intramural Research Program, National Institutes of Health, 5625 Fishers Lane, Room 3S-32:MSC 9412, Bethesda, MD 20892-9412, USA;11. Institute for Policy Research, Northwestern University, 2040 Sheridan Road, Evanston, IL 60208, USA;12. Institute for Innovations in Developmental Sciences, Northwestern University, 633 N Saint Clair, 19th Floor, Chicago, IL, 60611, USA;1. Department of Brain Biochemistry, Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland;2. Department of Pharmacokinetics and Drug Metabolism, Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland |
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| Abstract: | Studies were initiated to determine whether 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) affects circadian rhythms of serum prolactin (PRL), corticosterone, thyroxine (T4), and triiodothyronine (T3) in male Sprague-Dawley rats. In addition, the effects of TCDD on PRL receptor activity, as assessed by the ability of PRL to induce ornithine decarboxylase (ODC), were determined. The earliest effect detected following TCDD administration was a significant decrease in the serum PRL concentration compared with that of pair-fed controls within 4 hr (p less than 0.05). This was followed by a significant decrease in serum T4 by 6 hr (p less than 0.05). By 8 hr the serum peak of corticosterone was shifted to 2 hr later in the TCDD-treated rats. This temporal sequence of hormonal changes suggests that the earlier alteration in PRL may be involved in the later alterations in the concentrations of serum T4 and corticosterone. The serum PRL concentration 7 days after TCDD administration was significantly higher (p less than 0.05) in TCDD-treated animals compared with that in pair-fed controls (mean of 20.5 +/- 3.7 vs 13.6 +/- 1.8 ng/ml serum, p less than 0.05, respectively). The elevation of ODC activity in response to PRL, 2 days after TCDD, was decreased in the order of thymus greater than adrenal greater than spleen greater than heart greater than kidney greater than liver. By 7 days, liver ODC activity in response to PRL was only 12% that detected in pair-fed controls. Liver ODC activity in response to dexamethasone and aminophylline was decreased to 25 and 22% of pair-fed controls, respectively, by 7 days after TCDD administration. However, in kidney, TCDD-treated rats had an increased ODC response to aminophylline to 191% of pair-fed controls by Day 7. These results suggest that the ability of TCDD to alter receptor coupling or the receptor number for diverse hormones may play a role in TCDD toxicity. |
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