Adenosine stimulates connexin 43 expression and gap junctional communication in pituitary folliculostellate cells.
Adenosine is known to stimulate interleukin (IL)-6 and vascular endothelial growth factor (VEGF) secretion from pituitary TtT/GF folliculostellate [corrected] (FS) cells indicating that it is an important paracrine regulator of anterior pituitary function. This study demonstrates that rodent anterior pituitary cell lines produce extracellular adenosine that is able to increase intercellular gap junction communication in FS cells. Ecto-5'-nucleotidase (CD73), the enzyme that generates adenosine from AMP, was demonstrated by immunocytochemistry in approximately 20% of anterior pituitary cells, and some of these cells colocalized with prolactin and growth hormone. CD73 mRNA and protein were detected in GH3 and MMQ (somatotroph-lactotroph lineages) and TtT/GF cells, and enzyme activity was demonstrated by the conversion of exogenously added fluorescent ethenoAMP to ethenoadenosine. Adenosine production, as measured by HPLC, was detected in GH3 (1 microM/h) and MMQ (3 microM/h) but not in TtT/GF cells. Adenosine (EC50: 0.5 microM) and NECA (universal adenosine receptor agonist; EC50 0.1 microM) stimulated connexin 43 (Cx43) mRNA and protein expression within 1-2 h in TtT/GF cells. Adenosine and NECA also stimulated gap junctional intercellular communication (as assessed by transmission of Alexa Fluor 488) by 6- to 8-fold in comparison with untreated TtT/GF cells. In cocultures of MMQ and TtT/GF cells, Cx43 expression in TtT/GF cells increased in proportion to the number of MMQ cells plated out. These data suggest that adenosine, formed locally in the anterior pituitary gland can stimulate gap junction communication in FS cells.
Lewis
B Mary
BM
Centre for Endocrine and Diabetes Sciences, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.
Pexa
Annette
A
Francis
Karen
K
Verma
Vandana
V
McNicol
Anne M
AM
Scanlon
Maurice
M
Deussen
Andreas
A
Evans
W Howard
WH
Rees
D Aled
DA
Ham
Jack
J
D015720:5'-Nucleotidase / Q000378:metabolism; D000241:Adenosine / Q000378:metabolism*; D000243:Adenosine Deaminase / Q000378:metabolism; D000818:Animals; D002450:Cell Communication / Q000502:physiology*; D002478:Cells, Cultured; D018031:Connexin 43 / Q000378:metabolism*; D017629:Gap Junctions / Q000378:metabolism*; D005786:Gene Expression Regulation; D008297:Male; D051379:Mice; D010902:Pituitary Gland / Q000166:cytology*; D051381:Rats; D017208:Rats, Wistar
D018031:Connexin 43; D015720:5'-Nucleotidase; D000243:Adenosine Deaminase; D000241:Adenosine