Early expression of adenosine 5'-triphosphate-gated P2X7 receptors in the developing rat pancreas.
OBJECTIVE
Extracellular adenosine 5'-triphosphate modulates the functions of the adult pancreas via 2 nucleotide receptor families, the P2X and P2Y receptors. Expression of the P2X7 receptor has been demonstrated in islet cells of the pancreas, particularly the mature alpha cells that secrete glucagon. In the streptozotocin-induced diabetic model, a loss of insulin-secreting cells was accompanied by an increase in alpha cells that expressed the P2X7 receptor.


METHODS
In the present study, we have examined the expression of P2X7 receptors in the developing pancreas from embryonic days 10 (E10) to E18.


RESULTS
We detected P2X7 receptor-immunoreactive cells in pancreatic islet cells as early as E11' before glucagon expression. Subsequently, P2X7 receptors were expressed in glucagon-secreting cells at E12, and complete colocalization was observed at E14. Occasional colocalization of P2X7 receptors and insulin was observed in scattered cells at E12 and E14, but not at E18, when the glucagon- and insulin-secreting cells were almost completely segregated.


CONCLUSIONS
It was found that P2X7 receptors were expressed early in a subpopulation of glucagon- and insulin-immunopositive cells in developing islets and subsequently became restricted to glucagon-expressing cells as development proceeded. The possible functional significance of these changes is discussed.
Cheung
Kwok Kuen
KK
Autonomic Neuroscience Centre, Royal Free and University College Medical School, London, United Kingdom.
Coutinho-Silva
Robson
R
Chan
Wood Yee
WY
Burnstock
Geoffrey
G
D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D047108:Embryonic Development; D018507:Gene Expression Regulation, Developmental; D005934:Glucagon / Q000378:metabolism; D007150:Immunohistochemistry; D007328:Insulin / Q000032:analysis; D015640:Ion Channel Gating; D007515:Islets of Langerhans / Q000196:embryology; D010179:Pancreas / Q000196:embryology* / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000502:physiology*; D058486:Receptors, Purinergic P2X7
D007328:Insulin; C546470:P2rx7 protein, rat; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate; D005934:Glucagon