BES2005 Oral Communications Oral Communication 3: Neuroendocrinology (8 abstracts)
Adenosine expression and function in the anterior pituitary gland
K Francis 1 , A Pexa 2 , BM Lewis 1 , AM McNicol 3 , B Jasani 4 , A Deussen 2 , MF Scanlon 1 , DA Rees 1 & J Ham 1
1Centre for Endocrine and Diabetes Sciences, Cardiff University, Cardiff, UK; 2Institut fuer Physiologie, Medizinische Fakultaet Carl Gustav Carus, Dresden, Germany; 3Department of Pathology, The Royal Infirmary, Glasgow, UK; 4Department of Pathology, UHW, Cardiff, UK.
The nucleoside adenosine is an important regulator of interleukin-6 secretion from the folliculostellate (FS) cells of the anterior pituitary gland but the source of adenosine in this scenario is unknown. Therefore the aim of this study was to investigate secretion of adenosine and the expression of adenosine forming and metabolising enzymes in the pituitary gland.
Ecto-5/-nucleotidase (CD73), adenosine kinase and adenosine deaminase (AD) were detectable by RT-PCR in rat anterior pituitary and all rodent pituitary cell lines. Immunocytochemistry however showed that CD73 and AD are specifically associated with cells of lactotroph and somatotroph lineages in both rat and human pituitary tissue suggesting that adenosine is important in the function of these cells. Subsequent experiments were thus carried out in the MMQ (prolactin- secreting) and GH3 (prolactin and growth hormone-secreting) cell lines. The production of extracellular adenosine, as measured by fluorescent HPLC, were around 6-8 micromolar (MMQ) and 1-2 micromolar (GH3) per million cells per hour. CD73 enzyme activity was also determined in these cell lines where exogenously added fluorescent 1,N6-ethenoAMP was completely converted to 1,N6-ethenoadenosine within 2 hours.
The universal adenosine receptor agonist, NECA, inhibited forskolin stimulated prolactin secretion (radioimmunoassay) and slowed the rate of proliferation (as measured by MTS cell proliferation assay) in both MMQ and GH3 cells. On the other hand, western analysis suggests that NECA can increase the expression of connexin-43 within 2 hours.
In summary these data show that high levels of adenosine are released from lactotrophs and somatotrophs, either directly and/or by the metabolism of ATP where it may play a role in inhibiting cell growth and hormone release and stimulating gap junction formation. Adenosine is thus an important agent in the physiological control of the anterior pituitary and may also have a role in mediating its response to inflammation.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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