| Differential involvement of protein kinase C in basal versus acetylcholine-regulated prolactin secretion in rat anterior pituitary cells during aging. | |
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MedLine Citation:
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PMID: 12111996 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Although it is well known that plasma concentration of prolactin (PRL) increases during aging in rats, how the anterior pituitary (AP) aging per se affects PRL secretion remains obscure. The objectives of this study were to determine if changes in the pituitary PRL responsiveness to acetylcholine (ACh; a paracrine factor in the AP), as compared with that to other PRL stimulators or inhibitors, contribute to the known age-related increase in PRL secretion, and if protein kinase C (PKC) is involved. We also determined if replenishment with aging-declined hormones such as estrogen/thyroid hormone influences the aging-caused effects on pituitary PRL responses. AP cells were prepared from old (23-24-month-old) as well as young (2-3-month-old) ovariectomized rats. Cells were pretreated for 5 days with diluent or 17beta-estradiol (E(2); 0.6 nM) in combination with or without triiodothyronine (T(3); 10 nM). Then, cells were incubated for 20 min with thyrotropin-releasing hormone (TRH; 100 nM), angiotensin II (AII; 0.2-20 nM), vasoactive intestinal peptide (VIP; 10(-9)-10(-5) M), dopamine (DA; 10(-9)-10(-5) M), or ACh (10(-7)-10(-3) M). Cells were also challenged with ACh, TRH, or phorbol 12-myristate 13-acetate (PMA; 10(-6) M) following PKC depletion by prolonged PMA (10(-6) M for 24 h) pretreatment. We found that estrogen priming of AP cells could reverse the aging-caused effects on pituitary PRL responses to AII and DA. In hormone-replenished cells aging enhanced the stimulation of PRL secretion by TRH and PMA, but not by AII and VIP. Aging also reduced the responsiveness of cells to ACh and DA in suppressing basal PRL secretion, and attenuated ACh inhibition of TRH-induced PRL secretion. Furthermore, ACh suppressed TRH-induced PRL secretion mainly via the PMA-sensitive PKC in the old AP cells, but via additional mechanisms in young AP cells. On the contrary, basal PRL secretion was PKC (PMA-sensitive)-independent in the old AP cells, but dependent in the young AP cells. Taken together, these results suggest differential roles of PMA-sensitive PKC in regulating basal and ACh-regulated PRL responses in old versus young AP cells. The persistent aging-induced differences in AP cell responsiveness to ACh, DA, TRH, and PMA following hormone (E(2)/T(3)) replenishment suggest an intrinsic pituitary change that may contribute, in part, to the elevated in vivo PRL secretion observed in aged rats. |
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Authors:
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Hsiao-Fung Pu; Tsuei-Chu Liu |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Journal of cellular biochemistry Volume: 86 ISSN: 0730-2312 ISO Abbreviation: J. Cell. Biochem. Publication Date: 2002 |
Date Detail:
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Created Date: 2002-07-11 Completed Date: 2002-12-13 Revised Date: 2007-11-15 |
Medline Journal Info:
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Nlm Unique ID: 8205768 Medline TA: J Cell Biochem Country: United States |
Other Details:
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Languages: eng Pagination: 268-76 Citation Subset: IM |
Copyright Information:
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Copyright 2002 Wiley-Liss, Inc. |
Affiliation:
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Department of Physiology, School of Medicine, National Yang-Ming University, Shih-Pai, Taipei 112, Taiwan, Republic of China. hfpu@ym.edu.tw |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Acetylcholine
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pharmacology* Aging / physiology* Angiotensin II / pharmacology Animals Dopamine / pharmacology Female Pituitary Gland, Anterior / cytology*, metabolism*, secretion Prolactin / secretion* Protein Kinase C / deficiency, metabolism* Rats Rats, Sprague-Dawley Tetradecanoylphorbol Acetate / pharmacology Thyrotropin-Releasing Hormone / pharmacology Vasoactive Intestinal Peptide / pharmacology |
| Chemical | |
Reg. No./Substance:
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11128-99-7/Angiotensin II; 16561-29-8/Tetradecanoylphorbol Acetate; 24305-27-9/Thyrotropin-Releasing Hormone; 37221-79-7/Vasoactive Intestinal Peptide; 51-84-3/Acetylcholine; 9002-62-4/Prolactin; EC 2.7.11.13/Protein Kinase C |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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