Beta cell coupling and connexin expression change during the functional maturation of rat pancreatic islets.
OBJECTIVE
Cell-cell coupling mediated by gap junctions formed from connexin (CX) contributes to the control of insulin secretion in the endocrine pancreas. We investigated the cellular production and localisation of CX36 and CX43, and gap junction-mediated beta cell coupling in pancreatic islets from rats of different ages, displaying different degrees of maturation of insulin secretion.


METHODS
The presence and distribution of islet connexins were assessed by immunoblotting and immunofluorescence. The expression of connexin genes was evaluated by RT-PCR and quantitative real-time PCR. The ultrastructure of gap junctions and the function of connexin channels were assessed by freeze-fracture electron microscopy and tracer microinjection, respectively.


RESULTS
Young and adult beta cells, which respond to glucose, expressed significantly higher levels of Cx36 (also known as Gjd2) than fetal and newborn beta cells, which respond poorly to the sugar. Accordingly, adult beta cells also showed a significantly higher membrane density of gap junctions and greater intercellular exchange of ethidium bromide than newborn beta cells. Cx43 (also known as Gja1) was not expressed by beta cells, but was located in various cell types at the periphery of fetal and newborn islets.


CONCLUSIONS
These findings show that the pattern of connexins, gap junction membrane density and coupling changes in islets during the functional maturation of beta cells.
Carvalho
C P F
CP
Department of Histology and Embryology, Institute of Biology, University of Campinas (UNICAMP), Campinas, São Paulo, CEP 13083-970, Brazil.
Barbosa
H C L
HC
Britan
A
A
Santos-Silva
J C R
JC
Boschero
A C
AC
Meda
P
P
Collares-Buzato
C B
CB
D000818:Animals; D000831:Animals, Newborn; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D017629:Gap Junctions / Q000378:metabolism; D015151:Immunoblotting; D050417:Insulin-Secreting Cells / Q000378:metabolism* / Q000648:ultrastructure; D007515:Islets of Langerhans / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000097004:Gap Junction delta-2 Protein
D018031:Connexin 43; D017630:Connexins; D000097004:Gap Junction delta-2 Protein