Document Detail

Effects of lipocortin 1 and dexamethasone on the secretion of corticotrophin-releasing factors in the rat: in vitro and in vivo studies.
MedLine Citation:
PMID:  8485543     Owner:  NLM     Status:  MEDLINE    
Lipocortin 1 (LC1: also called annexin 1) was first described as a putative second messenger protein for the anti-inflammatory steroids in peripheral tissues. In the present study, in vitro and in vivo methods were used to examine its potential role within the hypothalamus as a mediator of the regulatory actions of the glucocorticoids on the hypothalamo-pituitary-adrenocortical axis of the rat. In the in vitro studies, the effects of human recombinant LC1 (hu-r-LC1) on the concomitant release of the two major corticotrophin-releasing factors (CRF-41 and arginine vasopressin, AVP) from isolated hypothalami removed from chronically adrenalectomized rats were compared with those of dexamethasone in the presence and absence of appropriate secretagogues, namely phospholipase A2 (PLA2), interleukin-6 (IL-6) and a non-specific depolarizing agent, K+ (56 mM). The spontaneous release of CRF-41 in vitro was unaffected by either hu-r-LC1 (5 to 100 ng/ml) or dexamethasone (1 microM). Both compounds however reduced the release of the neuropeptide evoked by IL-6 (5 ng/ml) but failed to modify the secretory responses to PLA2 (25 U/ml) or K+ (56 mM). Dexamethasone (1 microM) had no effect on the basal release of AVP but effectively blocked the secretion of the peptide induced by either IL-6 (10 ng/ml) or PLA2 (25 U/ml). In complete contrast, hu-r-LC1 (5 to 100 ng/ml) stimulated the release of AVP and potentiated the secretory responses to IL-6 (10 ng/ml) and PLA2 (25 U/ml) but not to K+ (56 mM). The hypothalamic responses to PLA2 stimulation (25 U/ml) were associated with significant (P < 0.01) increases in prostaglandin E2 release which, in some instances, were potentiated by hu-r-LC1 (5 to 20 ng/ml). In vivo, administration of histamine (0.6 mg/100 g body wt, ip) produced significant (P < 0.01) increases in the serum corticosterone concentration and in the hypothalamic LC1 content. Neither hu-r-LC1 (0.6 to 1.2 micrograms) nor a polyclonal anti-LC1 antibody (3 microliters, diluted 1:200), injected intracerebroventricularly (icv), influenced either the resting serum corticosterone concentration or the hypersecretion of the steroid evoked by histamine stress. A lower dose of the recombinant protein (0.3 micrograms icv) also failed to alter basal corticosterone release but, in contrast to the higher doses, potentiated the pituitary-adrenocortical responses to histamine. The results suggest that LC1 may contribute to some aspects of peptide release in the hypothalamus but that its actions are not necessarily related to those of the glucocorticoids.
H D Loxley; A M Cowell; R J Flower; J C Buckingham
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of neuroendocrinology     Volume:  5     ISSN:  0953-8194     ISO Abbreviation:  J. Neuroendocrinol.     Publication Date:  1993 Feb 
Date Detail:
Created Date:  1993-06-07     Completed Date:  1993-06-07     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  8913461     Medline TA:  J Neuroendocrinol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  51-61     Citation Subset:  IM    
Department of Pharmacology, Charing Cross and Westminster Medical School, London, UK.
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MeSH Terms
Annexin A1 / administration & dosage,  immunology,  pharmacology*
Antibodies, Monoclonal / immunology
Arginine Vasopressin / secretion
Corticotropin-Releasing Hormone / metabolism*
Dexamethasone / administration & dosage,  pharmacology*
Histamine / pharmacology
Hypothalamo-Hypophyseal System / drug effects,  physiology
Hypothalamus / drug effects,  metabolism
Injections, Intraventricular
Interleukin-6 / pharmacology
Phospholipases A / pharmacology
Phospholipases A2
Pituitary Gland, Posterior / drug effects,  metabolism
Potassium / pharmacology
Rats, Sprague-Dawley
Recombinant Proteins / pharmacology
Reg. No./Substance:
0/Annexin A1; 0/Antibodies, Monoclonal; 0/Interleukin-6; 0/Recombinant Proteins; 113-79-1/Arginine Vasopressin; 50-02-2/Dexamethasone; 51-45-6/Histamine; 7440-09-7/Potassium; 9015-71-8/Corticotropin-Releasing Hormone; EC 3.1.1.-/Phospholipases A; EC A2

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